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1.  Iron metabolism and risk of cancer in the Swedish AMORIS study 
Cancer Causes & Control  2013;24(7):1393-1402.
Objectives
Pre-clinical studies have shown that iron can be carcinogenic, but few population-based studies investigated the association between markers of the iron metabolism and risk of cancer while taking into account inflammation. We assessed the link between serum iron (SI), total-iron binding capacity (TIBC), and risk of cancer by levels of C-reactive protein (CRP) in a large population-based study (n = 220,642).
Methods
From the Swedish Apolipoprotein Mortality Risk (AMORIS) study, we selected all participants (>20 years old) with baseline measurements of serum SI, TIBC, and CRP. Multivariate Cox proportional hazards regression was carried out for standardized and quartile values of SI and TIBC. Similar analyses were performed for specific cancers (pancreatic, colon, liver, respiratory, kidney, prostate, stomach, and breast cancer). To avoid reverse causation, we excluded those with follow-up <3 years.
Results
We found a positive association between standardized TIBC and overall cancer [HR 1.03 (95 % CI 1.01–1.05)]. No statistically significant association was found between SI and cancer risk except for postmenopausal breast cancer [HR for standardized SI 1.09 (95 % CI 1.02–1.15)]. The association between TIBC and specific cancer was only statistically significant for colon cancer [i.e., HR for standardized TIBC: 1.17 (95 % CI 1.08–1.28)]. A borderline interaction between SI and levels of CRP was observed only in stomach cancer.
Conclusions
As opposed to pre-clinical findings for serum iron and cancer, this population-based epidemiological study showed an inverse relation between iron metabolism and cancer risk. Minimal role of inflammatory markers observed warrants further study focusing on developments of specific cancers.
doi:10.1007/s10552-013-0219-8
PMCID: PMC3675271  PMID: 23649231
Cancer; C-reactive protein; Iron; Iron-binding capacity; Sweden
2.  Biomarker-based score to predict mortality in persons aged 50 years and older: a new approach in the Swedish AMORIS study 
Background
Management of frailty is the cornerstone of geriatric medicine, but there remains a need to identify biomarkers that can predict early death, and thereby lead to effective clinical interventions. We aimed to study the combination of C-reactive protein (CRP), albumin, gamma-glutamyl transferase (GGT), and HDL to predict mortality.
Methods
A total of 44,457 persons aged 50+ whose levels of CRP, albumin, GGT, and HDL were measured at baseline were selected from the Swedish Apolipoprotein MOrtality RISk (AMORIS) study. A mortality score, ranging from 0 to 4, was created by adding the number of markers with abnormal values according to the clinical cut-off (CRP > 10 mg/L, albumin < 35 mg/L, GGT > 36 kU/L, HDL < 1.04 mmol/L). Mortality was studied with multivariate Cox proportional hazards models.
Results
2,245 persons died from cancer, 3,276 from circulatory disease, and 1,860 from other causes. There was a positive trend between mortality score and all-cause mortality as well as cancer and circulatory disease-specific death (e.g. HR for all-cause mortality: 1.39 (95%CI: 1.32-1.46), 2.04 (1.89-2.21), and 3.36 (2.87-3.93), for score=1, 2, and 3+, compared to score=0). Among cancer patients with no other co-morbidities (n=1,955), there was a positive trend between the score and mortality (HR: 1.24 (95%CI: 1.0.-1.49), 2.38 (95%CI: 1.76-3.22), and 5.47 (95%CI: 2.98-10.03) for score=1, 2, and 3+ compared to score=0).
Conclusions
By combining biomarkers of different mechanisms contributing to patient frailty, we found a strong marker for mortality in persons aged 50+. Elevated risks among cancer patients with no other co-morbidities prior to biomarker assessment call for validation in other cohorts and testing of different combinations and cut-offs than those used here, in order to aid decision-making in treatment of older cancer patients.
PMCID: PMC3316450  PMID: 22493753
Frailty; mortality; albumin; HDL-cholesterol; C-reactive protein; gamma-glutamyltransferase
3.  Lipid profiles and the risk of endometrial cancer in the Swedish AMORIS study 
Background
While the association between obesity and endometrial cancer (EC) is well established, the underlying mechanisms require further study. We assessed possible links between lipid profiles and EC risk, while also taking into account BMI, parity, and menopausal status at baseline.
Methods
Using the information available from the Swedish Apolipoprotein MOrtality RISk (AMORIS) study we created a cohort of 225,432 women with baseline values for glucose, triglycerides (TG), and total cholesterol (TC). Two subgroups of 31,792 and 26,317 had, in addition, baseline measurements of HDL, LDL, apolipoprotein A-I and apoB and BMI, respectively. We used Multivariate Cox proportional hazards models to analyze quartiles and dichotomized values of these lipid components for a link to EC risk.
Results
During mean follow-up of 12 years (SD: 4.15), 1,144 persons developed endometrial cancer. A statistically significant association was found between TG and EC risk when using both quartiles and a clinical cut-off (Hazard Ratio (HR): 1.10 (95%CI: 0.88-1.37), 1.34 (1.09-1.63), and 1.57 (1.28-1.92)) for the 2nd, 3rd, and 4th quartile, compared to the 1st, with P-value for trend: <0.001). The association remained after exclusion of the first three years of follow-up. Also total cholesterol and TG/HDL ratio were positively associated with EC risk, but no link was found for the other lipid components studied.
Conclusion
This detailed analysis of lipid components showed a consistent relation between TG levels and EC risk. Future research should continue to analyze the metabolic pathway and its relation to EC risk, as a pathway to further understand the relation of obesity and disease.
PMCID: PMC3376923  PMID: 22724049
Lipid profiles; risk factor; endometrial cancer; Swedish AMORIS study
4.  Serum calcium and risk of gastrointestinal cancer in the Swedish AMORIS study 
BMC Public Health  2013;13:663.
Background
Observational studies have indicated that high calcium intake may prevent colorectal cancer, but as for randomized trials the results are inconclusive. Meanwhile, limited data on the link between serum calcium and cancer risk is available. We investigated the relation between serum calcium and risk of different gastrointestinal cancers in a prospective study.
Methods
A cohort based on 492,044 subjects with baseline information on calcium (mmol/L) and albumin (g/L) was selected from the Swedish Apolipoprotein MOrtality RISk (AMORIS) study. Multivariable Cox proportional hazard models were used to analyse associations between standardised levels, quartiles and age/sex-specific categories of serum calcium and risk of oesophageal, stomach, colon, rectal cancer and also colorectal cancer combined, while taking into account serum albumin and other comorbidities.
Results
During 12 years of follow-up, we identified 323 incident oesophageal cancers, 782 stomach cancers, 2519 colon cancers, and 1495 rectal cancers. A positive association was found between albumin-adjusted serum calcium and risk of oesophageal [HR: 4.82 (95% CI: 2.07 – 11.19) for high compared to normal age-specific calcium levels] and colon cancer [e.g. HR: 1.07 (95% CI: 1.00 – 1.14) for every SD increase of calcium] as well as colorectal cancer [e.g. HR: 1.06 (95% CI: 1.02-1.11) for every SD increase of calcium] in women. In men there were similar but weaker non-statistically significant trends.
Conclusion
The positive relation between serum calcium, oesophageal cancer and colorectal cancer calls for further studies including calcium regulators to evaluate whether there is a true link between calcium metabolism and development of gastrointestinal cancer.
doi:10.1186/1471-2458-13-663
PMCID: PMC3729677  PMID: 23866097
Gastrointestinal cancer; Calcium; Albumin
5.  Inorganic phosphate and the risk of cancer in the Swedish AMORIS study 
BMC Cancer  2013;13:257.
Background
Both dietary and serum levels of inorganic phosphate (Pi) have been linked to development of cancer in experimental studies. This is the first population-based study investigating the relation between serum Pi and risk of cancer in humans.
Methods
From the Swedish Apolipoprotein Mortality Risk (AMORIS) study, we selected all participants (> 20 years old) with baseline measurements of serum Pi, calcium, alkaline phosphatase, glucose, and creatinine (n = 397,292). Multivariable Cox proportional hazards regression analyses were used to assess serum Pi in relation to overall cancer risk. Similar analyses were performed for specific cancer sites.
Results
We found a higher overall cancer risk with increasing Pi levels in men ( HR: 1.02 (95% CI: 1.00-1.04) for every SD increase in Pi), and a negative association in women (HR: 0.97 (95% CI: 0.96-0.99) for every SD increase in Pi). Further analyses for specific cancer sites showed a positive link between Pi quartiles and the risk of cancer of the pancreas, lung, thyroid gland and bone in men, and cancer of the oesophagus, lung, and nonmelanoma skin cancer in women. Conversely, the risks for developing breast and endometrial cancer as well as other endocrine cancer in both men and women were lower in those with higher Pi levels.
Conclusions
Abnormal Pi levels are related to development of cancer. Furthermore, the in verse association between Pi levels and risk of breast, endometrial and other endocrine cancers may indicate the role of hormonal factors in the relation between Pi metabolism and cancer.
doi:10.1186/1471-2407-13-257
PMCID: PMC3664604  PMID: 23706176
Cancer; Inorganic phosphate; Prospective cohort study
6.  Inflammation, Insulin Resistance, and Diabetes—Mendelian Randomization Using CRP Haplotypes Points Upstream 
PLoS Medicine  2008;5(8):e155.
Background
Raised C-reactive protein (CRP) is a risk factor for type 2 diabetes. According to the Mendelian randomization method, the association is likely to be causal if genetic variants that affect CRP level are associated with markers of diabetes development and diabetes. Our objective was to examine the nature of the association between CRP phenotype and diabetes development using CRP haplotypes as instrumental variables.
Methods and Findings
We genotyped three tagging SNPs (CRP + 2302G > A; CRP + 1444T > C; CRP + 4899T > G) in the CRP gene and measured serum CRP in 5,274 men and women at mean ages 49 and 61 y (Whitehall II Study). Homeostasis model assessment-insulin resistance (HOMA-IR) and hemoglobin A1c (HbA1c) were measured at age 61 y. Diabetes was ascertained by glucose tolerance test and self-report. Common major haplotypes were strongly associated with serum CRP levels, but unrelated to obesity, blood pressure, and socioeconomic position, which may confound the association between CRP and diabetes risk. Serum CRP was associated with these potential confounding factors. After adjustment for age and sex, baseline serum CRP was associated with incident diabetes (hazard ratio = 1.39 [95% confidence interval 1.29–1.51], HOMA-IR, and HbA1c, but the associations were considerably attenuated on adjustment for potential confounding factors. In contrast, CRP haplotypes were not associated with HOMA-IR or HbA1c (p = 0.52–0.92). The associations of CRP with HOMA-IR and HbA1c were all null when examined using instrumental variables analysis, with genetic variants as the instrument for serum CRP. Instrumental variables estimates differed from the directly observed associations (p = 0.007–0.11). Pooled analysis of CRP haplotypes and diabetes in Whitehall II and Northwick Park Heart Study II produced null findings (p = 0.25–0.88). Analyses based on the Wellcome Trust Case Control Consortium (1,923 diabetes cases, 2,932 controls) using three SNPs in tight linkage disequilibrium with our tagging SNPs also demonstrated null associations.
Conclusions
Observed associations between serum CRP and insulin resistance, glycemia, and diabetes are likely to be noncausal. Inflammation may play a causal role via upstream effectors rather than the downstream marker CRP.
Using a Mendelian randomization approach, Eric Brunner and colleagues show that the associations between serum C-reactive protein and insulin resistance, glycemia, and diabetes are likely to be noncausal.
Editors' Summary
Background.
Diabetes—a common, long-term (chronic) disease that causes heart, kidney, nerve, and eye problems and shortens life expectancy—is characterized by high levels of sugar (glucose) in the blood. In people without diabetes, blood sugar levels are controlled by the hormone insulin. Insulin is released by the pancreas after eating and “instructs” insulin-responsive muscle and fat cells to take up the glucose from the bloodstream that is produced by the digestion of food. In the early stages of type 2 diabetes (the commonest type of diabetes), the muscle and fat cells become nonresponsive to insulin (a condition called insulin resistance), and blood sugar levels increase. The pancreas responds by making more insulin—people with insulin resistance have high blood levels of both insulin and glucose. Eventually, however, the insulin-producing cells in the pancreas start to malfunction, insulin secretion decreases, and frank diabetes develops.
Why Was This Study Done?
Globally, about 200 million people have diabetes, but experts believe this number will double by 2030. Ways to prevent or delay the onset of diabetes are, therefore, urgently needed. One major risk factor for insulin resistance and diabetes is being overweight. According to one theory, increased body fat causes mild, chronic tissue inflammation, which leads to insulin resistance. Consistent with this idea, people with higher than normal amounts of the inflammatory protein C-reactive protein (CRP) in their blood have a high risk of developing diabetes. If inflammation does cause diabetes, then drugs that inhibit CRP might prevent diabetes. However, simply measuring CRP and determining whether the people with high levels develop diabetes cannot prove that CRP causes diabetes. Those people with high blood levels of CRP might have other unknown factors in common (confounding factors) that are the real causes of diabetes. In this study, the researchers use “Mendelian randomization” to examine whether increased blood CRP causes diabetes. Some variants of CRP (the gene that encodes CRP) increase the amount of CRP in the blood. Because these variants are inherited randomly, there is no likelihood of confounding factors, and an association between these variants and the development of insulin resistance and diabetes indicates, therefore, that increased CRP levels cause diabetes.
What Did the Researchers Do and Find?
The researchers measured blood CRP levels in more than 5,000 people enrolled in the Whitehall II study, which is investigating factors that affect disease development. They also used the “homeostasis model assessment-insulin resistance” (HOMA-IR) method to estimate insulin sensitivity from blood glucose and insulin measurements, and measured levels of hemoglobin A1c (HbA1c, hemoglobin with sugar attached—a measure of long-term blood sugar control) in these people. Finally, they looked at three “single polynucleotide polymorphisms” (SNPs, single nucleotide changes in a gene's DNA sequence; combinations of SNPs that are inherited as a block are called haplotypes) in CRP in each study participant. Common haplotypes of CRP were related to blood serum CRP levels and, as previously reported, increased blood CRP levels were associated with diabetes and with HOMA-IR and HbA1c values indicative of insulin resistance and poor blood sugar control, respectively. By contrast, CRP haplotypes were not related to HOMA-IR or HbA1c values. Similarly, pooled analysis of CRP haplotypes and diabetes in Whitehall II and another large study on health determinants (the Northwick Park Heart Study II) showed no association between CRP variants and diabetes risk. Finally, data from the Wellcome Trust Case Control Consortium also showed no association between CRP haplotypes and diabetes risk.
What Do These Findings Mean?
Together, these findings suggest that increased blood CRP levels are not responsible for the development of insulin resistance or diabetes, at least in European populations. It may be that there is a causal relationship between CRP levels and diabetes risk in other ethnic populations—further Mendelian randomization studies are needed to discover whether this is the case. For now, though, these findings suggest that drugs targeted against CRP are unlikely to prevent or delay the onset of diabetes. However, they do not discount the possibility that proteins involved earlier in the inflammatory process might cause diabetes and might thus represent good drug targets for diabetes prevention.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050155.
This study is further discussed in a PLoS Medicine Perspective by Bernard Keavney
The MedlinePlus encyclopedia provides information about diabetes and about C-reactive protein (in English and Spanish)
US National Institute of Diabetes and Digestive and Kidney Diseases provides patient information on all aspects of diabetes, including information on insulin resistance (in English and Spanish)
The International Diabetes Federation provides information about diabetes, including information on the global diabetes epidemic
The US Centers for Disease Control and Prevention provides information for the public and professionals on all aspects of diabetes (in English and Spanish)
Wikipedia has a page on Mendelian randomization (note: Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
doi:10.1371/journal.pmed.0050155
PMCID: PMC2504484  PMID: 18700811
7.  Serum Lipids and the Risk of Gastrointestinal Malignancies in the Swedish AMORIS Study 
Journal of Cancer Epidemiology  2012;2012:792034.
Background. Metabolic syndrome has been linked to an increased cancer risk, but the role of dyslipidaemia in gastrointestinal malignancies is unclear. We aimed to assess the risk of oesophageal, stomach, colon, and rectal cancers using serum levels of lipid components. Methods. From the Swedish Apolipoprotein Mortality Risk (AMORIS) study, we selected 540,309 participants (> 20 years old) with baseline measurements of total cholesterol (TC), triglycerides (TG), and glucose of whom 84,774 had baseline LDL cholesterol (LDL), HDL cholesterol (HDL), apolipoprotein B (apoB), and apolipoprotein A-I (apoA-I). Multivariate Cox proportional hazards regression was used to assess glucose and lipid components in relation to oesophageal, stomach, colon, and rectal cancer risk. Results. An increased risk of oesophageal cancer was observed in persons with high TG (e.g. HR: 2.29 (95% CI: 1.42–3.68) for the 4th quartile compared to the 1st) and low LDL, LDL/HDL ratio, TC/HDL ratio, log (TG/HDL), and apoB/apoA-I ratio. High glucose and TG were linked with an increased colon cancer risk, while high TC levels were associated with an increased rectal cancer risk. Conclusion. The persistent link between TC and rectal cancer risk as well as between TG and oesophageal and colon cancer risk in normoglycaemic individuals may imply their substantiality in gastrointestinal carcinogenesis.
doi:10.1155/2012/792034
PMCID: PMC3437288  PMID: 22969802
8.  A Genetic Association Study of Serum Acute-Phase C-Reactive Protein Levels in Rheumatoid Arthritis: Implications for Clinical Interpretation 
PLoS Medicine  2010;7(9):e1000341.
A genetic association study by Timothy Vyse and colleagues suggests that there is a significant association between CRP variants and acute-phase serum CRP concentrations in patients with rheumatoid arthritis, including those with chronic inflammation.
Background
The acute-phase increase in serum C-reactive protein (CRP) is used to diagnose and monitor infectious and inflammatory diseases. Little is known about the influence of genetics on acute-phase CRP, particularly in patients with chronic inflammation.
Methods and Findings
We studied two independent sets of patients with chronic inflammation due to rheumatoid arthritis (total 695 patients). A tagSNP approach captured common variation at the CRP locus and the relationship between genotype and serum CRP was explored by linear modelling. Erythrocyte sedimentation rate (ESR) was incorporated as an independent marker of inflammation to adjust for the varying levels of inflammatory disease activity between patients. Common genetic variants at the CRP locus were associated with acute-phase serum CRP (for the most associated haplotype: p = 0.002, p<0.0005, p<0.0005 in patient sets 1, 2, and the combined sets, respectively), translating into an approximately 3.5-fold change in expected serum CRP concentrations between carriers of two common CRP haplotypes. For example, when ESR = 50 mm/h the expected geometric mean CRP (95% confidence interval) concentration was 43.1 mg/l (32.1–50.0) for haplotype 1 and 14.2 mg/l (9.5–23.2) for haplotype 4.
Conclusions
Our findings raise questions about the interpretation of acute-phase serum CRP. In particular, failure to take into account the potential for genetic effects may result in the inappropriate reassurance or suboptimal treatment of patients simply because they carry low-CRP–associated genetic variants. CRP is increasingly being incorporated into clinical algorithms to compare disease activity between patients and to predict future clinical events: our findings impact on the use of these algorithms. For example, where access to effective, but expensive, biological therapies in rheumatoid arthritis is rationed on the basis of a DAS28-CRP clinical activity score, then two patients with identical underlying disease severity could be given, or denied, treatment on the basis of CRP genotype alone. The accuracy and utility of these algorithms might be improved by using a genetically adjusted CRP measurement.
Please see later in the article for the Editors' Summary
Editors' Summary
C-reactive protein (CRP) is a serum marker for inflammation or infection and acts by binding to a chemical (phosphocholine) found on the surface of dead or dying cells (and some types of bacteria) in order to activate the immune system (via the complement system). Fat cells release factors that stimulate the liver to produce CRP, and serum levels greater than 10 mg/l are generally considered indicative of an infectious or inflammatory process. After an inflammatory stimulus, serum CRP levels may exceed 500 times baseline, so CRP is used in all medical specialities to help diagnose inflammation and infection. Although patients with chronic inflammatory diseases, such as rheumatoid arthritis, have raised levels of CRP, levels of CRP are still highly variable. Some studies have suggested that there may be genetic variations of CRP (CRP variants) that determine the magnitude of the acute-phase CRP response, a finding that has important clinical implications: CRP thresholds are used as a diagnostic component of formal clinical algorithms and play an important role in a clinician's decision-making process when diagnosing inflammatory disease and choosing treatment options. Therefore, it is possible that false reassurance could be given to a patient with disease, or optimal treatment withheld, because some patients are genetically predisposed to have only a modest increase in acute-phase CRP.
Why Was This Study Done?
Although some studies have looked at the CRP gene variant response, few, if any, studies have examined the CRP gene variant response in the context of chronic inflammation, such as in rheumatoid arthritis. Therefore, this study aimed to determine whether CRP gene variants could also influence CRP serum levels in rheumatoid arthritis.
What Did the Researchers Do and Find?
The authors studied two independent sets of patients with chronic inflammation due to rheumatoid arthritis (total 695 patients): one patient set used a cohort of 281 patients in the UK, and the other patient set (used for replication) consisted of 414 patients from New Zealand and Australia. A genetic technique (a tagSNP approach) was used to capture common variations at the CRP locus (haplotype association analysis) at both the population and the individual level. The relationship between genotype and serum CRP was explored by linear modeling. The researchers found that common genetic variants at the CRP locus were associated with acute-phase serum CRP in both patient sets translating into an approximate 3.5-fold change in expected serum CRP between carriers of two common CRP variants. For example, when ESR = 50 mm/h the expected CRP serum level for one common CRP variant was 43.1 mg/l and for another CRP variant was 14.2 mg/l.
What Do These Findings Mean?
The findings of this study raise questions about the interpretation of acute-phase serum CRP, as they suggest that there is a significant association between CRP variants and acute-phase serum CRP concentrations in a group of patients with rheumatoid arthritis, including those with chronic active inflammation. The size of the genetic effect may be large enough to have a clinically relevant impact on the assessment of inflammatory disease activity, which in turn may influence therapeutic decision making. Failure to take into account the potential for genetic effects may result in the inappropriate reassurance or undertreatment of patients simply because they carry low-CRP–associated genetic variants. CRP is increasingly being incorporated into clinical algorithms to compare disease activity between patients and to predict future clinical events, so these findings impact on the use of such algorithms. The accuracy and utility of these algorithms might be improved by using a genetically adjusted CRP measurement.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000341
Lab Test Online provides information on CRP
The Wellcome Trust provides a glossary of genetic terms
Learn.Genetics provides access to the Genetic Science Learning Center, which is part of the human genome project
doi:10.1371/journal.pmed.1000341
PMCID: PMC2943443  PMID: 20877716
9.  Plasma C-reactive protein, genetic risk score, and risk of common cancers in the Atherosclerosis Risk in Communities study 
Cancer causes & control : CCC  2013;24(12):10.1007/s10552-013-0285-y.
Purpose
Many studies, including the Atherosclerosis Risk in Communities (ARIC) cohort, reported a positive association between plasma C-reactive protein (CRP) – a biomarker of low-grade chronic inflammation – and colorectal cancer risk, although it is unclear if the association is causal. Our aims were to assess the associations of a CRP genetic risk score (CRP-GRS) created from single nucleotide polymorphisms (SNPs) with colorectal cancer risk, as well as examine plasma CRP and CRP-GRS in relation to common cancers in the ARIC cohort.
Methods
Cox proportional hazards models were used to prospectively estimate hazard ratios (HR) and (95% confidence interval, CI) of total, colorectal, lung, prostate, and breast cancers in relation to: 1) CRP-GRS among 8,657 Whites followed in 1987–2006 and 2) log-transformed plasma CRP among 7,603 Whites followed in 1996–2006. A weighted CRP-GRS was comprised of 20 CRP-related SNPs located in/near CRP, APOC1, HNF1A, LEPR and 16 other genes that were identified in genome-wide association studies.
Results
After multivariable adjustment, one standard deviation increment of the CRP-GRS was associated with colorectal cancer risk (HR=1.19; 95% CI, 1.03–1.37) but not with any other cancer. One unit of log-transformed plasma CRP was associated with the risk of total, colorectal, lung, and breast cancers: HRs (95% CIs) were 1.08 (1.01–1.15), 1.24 (1.01–1.51), 1.29 (1.08–1.54), and 1.27 (1.07–1.51), respectively. HRs remained elevated, although lost statistical significance for all but breast cancer, after excluding subjects with <2 years of follow-up.
Conclusions
The study corroborates a causative role of chronic low-grade inflammation in colorectal carcinogenesis.
doi:10.1007/s10552-013-0285-y
PMCID: PMC3836434  PMID: 24036889
inflammation; CRP; cancer risk; genetic risk score; genetic polymorphism; ARIC cohort
10.  Three-Year Change in Inflammatory Markers in Elderly People and Mortality: The Invecchiare in Chianti Study 
Objectives
To describe changes in interleukin-6 (IL-6) and C-reactive protein (CRP) and to determine how changes are related to mortality in elderly people.
Design
Prospective cohort study.
Setting
Two communities in the Tuscany region of Italy.
Participants
Randomly selected residents aged 65 and older who participated in the first two waves of data collection (N = 736).
Measurements
Two serum measurements of IL-6 and CRP taken 3 years apart. Mortality was observed for the 3 years after the second measurement; 79 deaths were observed in 2,079 person-years.
Results
Correlations indicated marginal to moderate stability in IL-6 and CRP, with clinical categories remaining relatively stable over time. Baseline levels were not related to mortality between follow-up Years 3 and 6, but increases in IL-6 and CRP predicted 3- to 6-year mortality. Controlling for follow-up IL-6 and CRP attenuated the relationship between inflammatory changes and mortality, but increases in CRP continued to increase odds of mortality. After controlling for sociodemographic characteristics, biological risk factors, health behaviors, and disease at both times, increases in CRP, but not IL-6, were related to mortality. Odds of death were more than three times as great in subjects in whom any CRP increase was observed (odds ratio = 3.10, 95% confidence interval = 1.25–7.68) as in subjects with stable or declining CRP.
Conclusion
CRP and IL-6 levels within individuals vary over time, and increases in CRP are associated with greater mortality risk. Three-year changes in inflammatory markers are better predictors of mortality than baseline measures.
doi:10.1111/j.1532-5415.2007.01390.x
PMCID: PMC2646097  PMID: 17727645
aging; epidemiology; interleukins
11.  High-Sensitivity C-Reactive Protein and Ankle Brachial Index in a Finnish Cardiovascular Risk Population 
High-sensitivity C-reactive protein (hsCRP) has been previously linked to different forms of vascular disease. However, some studies have not found any relationship between hsCRP and atherosclerosis. Also, studies investigating correlation between hsCRP and ankle brachial index (ABI) are scarce. We studied hsCRP in a cardiovascular risk population with a special interest in correlation between hsCRP and ABI. All men and women aged 45 to 70 years from a rural town Harjavalta, Finland were invited to participate in a population survey. Diabetics and people with known vascular disease were excluded. Seventy-three percent (n = 2085) of the invited persons participated and 70% of the respondents (n = 1496) had at least one risk factor to cardiovascular diseases. These subjects were invited to further examinations. From them we measured ABI, hsCRP, leukocyte count, glucose tolerance, systemic coronary risk evaluation (SCORE), body mass index (BMI), and waist circumference. Mean hsCRP was 1.9 mg/L. Smokers had higher hsCRP (mean 2.2 mg/L) than nonsmokers (mean 1.8 mL/L). hsCRP in women was higher than in men (mean 2.0 mg/L versus 1.8 mg/L). Mean ABI was 1.10, and the prevalence of peripheral arterial disease was 3.1%. ABI correlated weakly with hsCRP (r = −0.077, p = 0.014), leukocyte count (r = −0.107, p = 0.001), and SCORE (r = −0.116, p = 0.001). It did not have correlation between age, weight, BMI, or waist circumference. hsCRP correlated with BMI (r = 0.208, p < 0.0001) and waist circumference (r = 0.325, p < 0.0001). When we excluded subjects with hsCRP >10 mg/L, ABI no longer correlated with hsCRP. In a cardiovascular risk population, hsCRP has only a weak correlation with ABI, and this correlation disappeared when we excluded subject with hsCRP >10 mg/L. Instead, hsCRP was correlated to the measures of obesity (waist circumference and BMI), indicating its role as a marker of adipose tissue–driven inflammation. hsCRP does not seem to be a suitable screening method for peripheral arterial disease.
doi:10.1055/s-0031-1272551
PMCID: PMC3331626  PMID: 22532770
High sensitivity C-reactive protein; ankle brachial index; cardiovascular risk factors
12.  High-Sensitivity CRP Is an Independent Risk Factor for All Fractures and Vertebral Fractures in Elderly Men: The MrOS Sweden Study 
Epidemiological studies have shown low-grade inflammation measured by high-sensitivity C-reactive protein (hs-CRP) to be associated with fracture risk in women. However, it is still unclear whether hs-CRP is also associated with fracture risk in men. We therefore measured serum levels of hs-CRP in 2910 men, mean age 75 years, included in the prospective population-based MrOS Sweden cohort. Study participants were divided into tertile groups based on hs-CRP level. Fractures occurring after the baseline visit were validated (average follow-up 5.4 years). The incidence for having at least one fracture after baseline was 23.9 per 1000 person-years. In Cox proportional hazard regression analyses adjusted for age, hs-CRP was related to fracture risk. The hazard ratio (HR) of fracture for the highest tertile of hs-CRP, compared with the lowest and the medium tertiles combined, was 1.48 (95% CI, 1.20–1.82). Multivariate adjustment for other risk factors for fractures had no major effect on the associations between hs-CRP and fracture. Results were essentially unchanged after exclusion of subjects with hs-CRP levels greater than 7.5 mg/L, as well as after exclusion of subjects with a first fracture within 3 years of follow-up, supporting that the associations between hs-CRP and fracture risk were not merely a reflection of a poor health status at the time of serum sampling. Femoral neck bone mineral density (BMD) was not associated with hs-CRP, and the predictive role of hs-CRP for fracture risk was essentially unchanged when femoral neck BMD was added to the model (HR, 1.37; 95% CI, 1.09–1.72). Exploratory subanalyses of fracture type demonstrated that hs-CRP was clearly associated with clinical vertebral fractures (HR, 1.61; 95% CI, 1.12–2.29). We demonstrate, using a large prospective population-based study, that elderly men with high hs-CRP have increased risk of fractures, and that these fractures are mainly vertebral. The association between hs-CRP and fractures was independent of BMD.
doi:10.1002/jbmr.2037
PMCID: PMC4238816  PMID: 23857741
FRACTURE RISK; AGING, DXA; LOW GRADE INFLAMMATION; hs-CRP
13.  High-Sensitivity C-Reactive Protein and Cancer 
Journal of Epidemiology  2011;21(3):161-168.
Background
High-sensitivity C-reactive protein (hs-CRP) is a commonly used inflammatory marker. The association between hs-CRP and cancer is less consistent than that between hs-CRP and cardiovascular diseases. This study explored the association between hs-CRP and cancer, using a large database of Korean health examination records.
Methods
A total of 80 781 Koreans who visited the health promotion center of a general hospital were included. There were 729 cases of cancer of any primary site during a 3-year period. Subjects with a known cancer or a condition capable of affecting hs-CRP were excluded.
Results
Serum hs-CRP was significantly higher in cancer cases (2.9 mg/L) than in non-cases (1.4 mg/L; P < 0.0001). With the lowest hs-CRP category (<1 mg/L) as reference, the crude odds ratios (ORs) for cancer were 1.36 (95% confidence interval [CI] = 1.16–1.62) for the second highest category (1–3 mg/L) and 2.49 (95% CI = 2.02–3.07) for the highest category (>3 mg/L), and the adjusted ORs for cancer were 1.16 (95% CI = 0.95–1.42) for the second highest category and 1.94 (95% CI = 1.51–2.51) for the highest category. After excluding cancer cases detected within 1 year after the check-up, the associations remained, although the reduced number of cancer cases (n = 88) attenuated the significance of the associations.
Conclusions
Serum hs-CRP was positively associated with the risk of cancer, although causality cannot be inferred in this cross-sectional study. The results support the hypothesis that chronic inflammation plays a role in cancer.
doi:10.2188/jea.JE20100128
PMCID: PMC3899404  PMID: 21368452
high-sensitivity C-reactive protein; cancer; inflammation
14.  Predicting risk of cancer during HIV infection: the role of inflammatory and coagulation biomarkers 
AIDS (London, England)  2013;27(9):1433-1441.
Objective
To investigate the relationship between inflammatory [interleukin-6 (IL-6) and C-reactive protein (CRP)] and coagulation (D-dimer) biomarkers and cancer risk during HIV infection.
Design
A prospective cohort.
Methods
HIV-infected patients on continuous antiretroviral therapy (ART) in the control arms of three randomized trials (N = 5023) were included in an analysis of predictors of cancer (any type, infection-related or infection-unrelated). Hazard ratios for IL-6, CRP and D-dimer levels (log2-transformed) were calculated using Cox models stratified by trial and adjusted for demographics and CD4+ cell counts and adjusted also for all biomarkers simultaneously. To assess the possibility that biomarker levels were elevated at entry due to undiagnosed cancer, analyses were repeated excluding early cancer events (i.e. diagnosed during first 2 years of follow-up).
Results
During approximately 24 000 person-years of follow-up (PYFU), 172 patients developed cancer (70 infection-related; 102 infection-unrelated). The risk of developing cancer was associated with higher levels (per doubling) of IL-6 (hazard ratio 1.38, P < 0.001), CRP (hazard ratio 1.16, P = 0.001) and D-dimer (hazard ratio 1.17, P = 0.03). However, only IL-6 (hazard ratio 1.29, P = 0.003) remained associated with cancer risk when all biomarkers were considered simultaneously. Results for infection-related and infection-unrelated cancers were similar to results for any cancer. Hazard ratios excluding 69 early cancer events were 1.31 (P = 0.007), 1.14 (P = 0.02) and 1.07 (P = 0.49) for IL-6, CRP and D-dimer, respectively.
Conclusion
Activated inflammation and coagulation pathways are associated with increased cancer risk during HIV infection. This association was stronger for IL-6 and persisted after excluding early cancer. Trials of interventions may be warranted to assess whether cancer risk can be reduced by lowering IL-6 levels in HIV-positive individuals.
doi:10.1097/QAD.0b013e32835f6b0c
PMCID: PMC4046103  PMID: 23945504
biomarkers; cancer; C-reactive protein; D-dimer; HIV; interleukin-6
15.  Biomarkers of inflammation are associated with colorectal cancer risk in women but are not suitable as early detection markers 
Initial studies have investigated the association between inflammation and colorectal cancer (CRC) using C-reactive protein (CRP) as a pro-inflammatory biomarker and have noted inconsistent results among women. We here report findings from a large prospective study with repeat measurements of CRP, as well as serum-amyloid A (SAA), an additional biomarker of inflammation, and risk of CRC. In the Women’s Health Initiative Observational Study, we examined associations of CRP and SAA with CRC using repeat assessments (baseline and 3-year follow-up) among 953 matched case-control pairs for CRP and 966 pairs for SAA. Multivariate-adjusted conditional-logistic regression models were used with two-sided tests of significance. Receiver operating characteristic (ROC) curve analysis assessed their utility as early detection markers. Colon cancer risk (odds ratio, OR, and 95% confidence intervals) among women in the highest quintiles of CRP or SAA compared to those in the lowest quintiles was ORcolon/CRP=1.37 (0.95-1.97, p-trend=0.04) and ORcolon/SAA=1.26 (0.88-1.80, p-trend=0.10), respectively. Women with elevated concentrations of both CRP and SAA had an increased risk of ORcolon=1.50 (1.12-2.00, p-value=0.006) compared to those with low concentrations. No positive associations were observed with rectal cancer and weaker associations for CRC overall. Temporal changes in biomarkers over 3-years did not predict risk. The area under the 6-month ROC curve for CRP+SAA was 0.62 (95%CI 0.55-0.68). Elevated inflammatory biomarkers are associated with an increased risk of CRC, mainly colon cancer. Nevertheless, changes in the biomarkers over time do not suggest that they merit consideration as early-detection markers for CRC.
doi:10.1002/ijc.27942
PMCID: PMC3609926  PMID: 23161620
C-reactive protein (CRP); serum amyloid A (SAA); colorectal cancer; women; early detection
16.  C-reactive Protein and Risk of Colorectal Adenoma According to Celecoxib Treatment 
Background
Inflammation, as measured by the circulating inflammatory marker high sensitivity C-reactive protein (hsCRP), has been associated with cardiovascular disease. However, data regarding CRP and risk of colorectal cancer have been conflicting. The Adenoma Prevention with Celecoxib (APC) trial demonstrated that the anti-inflammatory drug celecoxib prevents recurrence of colorectal adenoma but increases risk of cardiovascular events. We examined if serum hsCRP modified these results.
Methods
We measured hsCRP from serum specimens provided at study entry by patients enrolled in the APC trial. Patients were stratified according to use of low-dose aspirin, randomized to receive three years of treatment with placebo, 200-mg-bid celecoxib, or 400-mg-bid celecoxib, and underwent follow-up colonoscopies at Year 1 and 3.
Results
Among 1,680 patients, the estimated three-year cumulative incidence of adenoma was 42% for patients with hsCRP <1mg/L, compared with 43% (RR=1.02; 95% confidence interval (CI)=0.85–1.22) for hsCRP 1–3mg/L, and 41% (RR=1.1; CI=0.90–1.34) for hsCRP >3mg/L. The effect of celecoxib on adenoma recurrence did not vary among patients with high (>3mg/L) compared with low (≦3mg/L) hsCRP. However, among patients with high hsCRP, the RR of cardiovascular events compared with placebo was 2.27 (95%CI=0.72–7.14) for those randomized to celecoxib 200-mg-bid and 3.28 (CI=1.09–9.91) for 400-mg-bid. In contrast, among patients with low hsCRP, the corresponding RRs were 0.99 (CI=0.53–1.83) and 1.11 (CI=0.61–2.02).
Conclusions
HsCRP may predict risk of celecoxib-associated cardiovascular toxicity, but not adenoma recurrence or celecoxib treatment efficacy. Patients with low hsCRP may be a subgroup with a favorable risk-benefit profile for celecoxib chemoprevention.
doi:10.1158/1940-6207.CAPR-10-0403
PMCID: PMC3151679  PMID: 21816845
Adenoma; celecoxib; c-reactive protein; inflammation; chemoprevention
17.  Fructosamine Is a Useful Indicator of Hyperglycaemia and Glucose Control in Clinical and Epidemiological Studies – Cross-Sectional and Longitudinal Experience from the AMORIS Cohort 
PLoS ONE  2014;9(10):e111463.
Context
Fructosamine is a glycemic biomarker which may be useful for indication and control of diabetes respectively.
Objective
The objective of the study was to evaluate fructosamine as an indicator of hyperglycaemia and glucose control in subjects with diabetes.
Design, Setting & Patients
From the AMORIS cohort, subjects with serum glucose, fructosamine and HbA1c from the same examination were studied cross-sectionally and longitudinally (n = 10,987; 5,590 overnight-fasting). The guidelines of the American Diabetes Association were followed for classification of prediabetes and diabetes. Separate analyses were performed in patients with a newly detected or a known diagnosis of type 1 or type 2 diabetes respectively.
Results
All three biomarkers were strongly correlated. With regard to the association between fructosamine and HbA1c Pearson linear correlation coefficients in the range of 0.67–0.75 were observed in fasting and non-fasting subjects with type 1 or type 2 diabetes. Analyses of glucose control in fasting patients with type 2 diabetes having all three biomarkers measured at three separate occasions within on average 290 days of the index examination showed similar trends over time for glucose, fructosamine and HbA1c. Discrimination of subjects with and without diabetes across the range of fructosamine levels was good (area under curve (AUC) 0.91–0.95) and a fructosamine level of 2.5 mmol/L classified subjects to diabetes with a sensitivity of 61% and a specificity of 97%.
Conclusions
Fructosamine is closely associated with HbA1c and glucose respectively and may be a useful biomarker of hyperglycaemia and glucose control in clinical and epidemiological studies.
doi:10.1371/journal.pone.0111463
PMCID: PMC4213035  PMID: 25353659
18.  Effects of a caloric restriction weight loss diet and exercise on inflammatory biomarkers in overweight/obese postmenopausal women: a randomized controlled trial 
Cancer Research  2012;72(9):2314-2326.
Obese and sedentary persons have increased risk for cancer; inflammation is a hypothesized mechanism. We examined the effects of a caloric restriction weight loss diet and exercise on inflammatory biomarkers in 439 women. Overweight and obese postmenopausal women were randomized to 1-year: caloric restriction diet (goal of 10% weight loss, N=118), aerobic exercise (225 minutes/week of moderate-to-vigorous activity, N=117), combined diet+exercise (N=117) or control (N=87). Baseline and 1-year high-sensitivity C-reactive protein (hs-CRP), serum amyloid A (SAA), interleukin-6 (IL-6), leukocyte and neutrophil levels were measured by investigators blind to group. Inflammatory biomarker changes were compared using generalized estimating equations. Models were adjusted for baseline body mass index (BMI), race/ethnicity and age. 438 (N=1 in diet+exercise group was excluded) were analyzed. Relative to controls, hs-CRP decreased by geometric mean (95% confidence interval, p-value) 0.92mg/L (0.53–1.31, P<0.001) in the diet and 0.87mg/L (0.51–1.23, P<0.0001) in the diet+exercise groups. IL-6 decreased by 0.34pg/ml (0.13–0.55, P=0.001) in the diet and 0.32pg/ml (0.15–0.49, P<0.001) in the diet+exercise groups. Neutrophil counts decreased by 0.31×109/L (0.09–0.54, P=0.006) in the diet and 0.30×109/L (0.09–0.50, P=0.005) in the diet+exercise groups. Diet and diet+exercise participants with ≥5% weight loss reduced inflammatory biomarkers (hs-CRP, SAA, and IL-6) compared to controls. The diet and diet+exercise groups reduced hs-CRP in all subgroups of baseline BMI, waist circumference, CRP level, and fasting glucose. Our findings indicate that a caloric restriction weight loss diet with or without exercise reduces biomarkers of inflammation in postmenopausal women, with potential clinical significance for cancer risk reduction.
doi:10.1158/0008-5472.CAN-11-3092
PMCID: PMC3342840  PMID: 22549948
inflammation; postmenopausal women; obesity; exercise; dietary weight loss
19.  Intraindividual variability of C-reactive protein: The Multi-Ethnic Study of Atherosclerosis 
Atherosclerosis  2012;224(1):274-279.
Background
The intraindividual variability of C-reactive protein (CRP) remains uncertain. Although guidelines suggest stability of serial CRP values comparable to that of cholesterol measures, several studies indicate greater fluctuations of CRP. We sought to compare the intraindividual variability of CRP with that of cholesterol measures using the Multi-Ethnic Study of Atherosclerosis (MESA).
Methods
CRP measurements were available in 760 MESA participants after exclusion of those with comorbidities or medications known to affect CRP or CRP≥10 mg/L. Serial values were available for 255 participants. The intraclass correlation coefficient (ICC) was quantified for CRP, total cholesterol (TC), and non-HDL-cholesterol (non-HDL-C) as the ratio of between-subject variance to the sum of between-subject and within-subject variance. Fluctuation between baseline and follow-up categories was calculated by cross-classifying participants according to baseline tertiles.
Results
The multivariable-adjusted ICC of CRP was 0.62 (95% CI, 0.55–0.68), significantly lower than that of TC (0.75; 95% CI, 0.70–0.81; p=0.001 vs CRP) and non-HDL-C (0.76; 95% CI, 0.71–0.81; p=0.001 vs CRP). 51% of participants in the highest baseline CRP tertile had discordant values on follow-up, while 54% and 27% were discordant in the middle and lowest baseline CRP tertiles. Among participants with baseline CRP levels exceeding 3 mg/L, a clinical threshold for higher risk, 69% had subsequent measurements falling within a lower risk category.
Conclusions
In the MESA cohort, intraindividual variation of CRP was significantly greater than that for cholesterol measures. Our results suggest that further evaluation of CRP variability is needed in large prospective studies using shorter intervals between measurements.
doi:10.1016/j.atherosclerosis.2012.07.017
PMCID: PMC4085141  PMID: 22846611
20.  Evaluating the Quality of Research into a Single Prognostic Biomarker: A Systematic Review and Meta-analysis of 83 Studies of C-Reactive Protein in Stable Coronary Artery Disease 
PLoS Medicine  2010;7(6):e1000286.
In a systematic review and meta-analysis of 83 prognostic studies of C-reactive protein in coronary disease, Hemingway and colleagues find substantial biases, preventing them from drawing clear conclusions relating to the use of this marker in clinical practice.
Background
Systematic evaluations of the quality of research on a single prognostic biomarker are rare. We sought to evaluate the quality of prognostic research evidence for the association of C-reactive protein (CRP) with fatal and nonfatal events among patients with stable coronary disease.
Methods and Findings
We searched MEDLINE (1966 to 2009) and EMBASE (1980 to 2009) and selected prospective studies of patients with stable coronary disease, reporting a relative risk for the association of CRP with death and nonfatal cardiovascular events. We included 83 studies, reporting 61,684 patients and 6,485 outcome events. No study reported a prespecified statistical analysis protocol; only two studies reported the time elapsed (in months or years) between initial presentation of symptomatic coronary disease and inclusion in the study. Studies reported a median of seven items (of 17) from the REMARK reporting guidelines, with no evidence of change over time.
The pooled relative risk for the top versus bottom third of CRP distribution was 1.97 (95% confidence interval [CI] 1.78–2.17), with substantial heterogeneity (I2 = 79.5). Only 13 studies adjusted for conventional risk factors (age, sex, smoking, obesity, diabetes, and low-density lipoprotein [LDL] cholesterol) and these had a relative risk of 1.65 (95% CI 1.39–1.96), I2 = 33.7. Studies reported ten different ways of comparing CRP values, with weaker relative risks for those based on continuous measures. Adjusting for publication bias (for which there was strong evidence, Egger's p<0.001) using a validated method reduced the relative risk to 1.19 (95% CI 1.13–1.25). Only two studies reported a measure of discrimination (c-statistic). In 20 studies the detection rate for subsequent events could be calculated and was 31% for a 10% false positive rate, and the calculated pooled c-statistic was 0.61 (0.57–0.66).
Conclusion
Multiple types of reporting bias, and publication bias, make the magnitude of any independent association between CRP and prognosis among patients with stable coronary disease sufficiently uncertain that no clinical practice recommendations can be made. Publication of prespecified statistical analytic protocols and prospective registration of studies, among other measures, might help improve the quality of prognostic biomarker research.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
Coronary artery disease is the leading cause of death among adults in developed countries. With age, fatty deposits called atherosclerotic plaques coat the walls of the arteries, the vessels that carry blood to the body's organs. Because they narrow the arteries, atherosclerotic plaques restrict blood flow. If plaques form in the arteries that feed the heart, the result is coronary artery disease, the symptoms of which include shortness of breath and chest pains (angina). If these symptoms only occur during exertion, the condition is called stable coronary artery disease. Coronary artery disease can cause potentially fatal heart attacks (myocardial infarctions). A heart attack occurs when a plaque ruptures and a blood clot completely blocks the artery, thereby killing part of the heart. Smoking, high blood pressure, high blood levels of cholesterol (a type of fat), diabetes, and being overweight are risk factors for coronary artery disease. Treatments for the condition include lifestyle changes and medications that lower blood pressure and blood cholesterol. Narrowed arteries can also be widened using a device called a stent or surgically bypassed.
Why Was This Study Done?
Clinicians can predict whether a patient with coronary artery disease is likely to have a heart attack by considering their risk factors. They then use this “prognosis” to help them manage the patient. To provide further help for clinicians, researchers are trying to identify prognostic biomarkers (molecules whose blood levels indicate how a disease might develop) for coronary artery disease. However, before a biomarker can be used clinically, it must be properly validated and there are concerns that there is insufficient high quality evidence to validate many biomarkers. In this systematic review and meta-analysis, the researchers ask whether the evidence for an association between blood levels of C-reactive protein (CRP, an inflammatory protein) and subsequent fatal and nonfatal events affecting the heart and circulation (cardiovascular events) among patients with stable coronary artery disease supports the routine measurement of CRP as recommended in clinical practice guidelines. A systematic review uses predefined criteria to identify all the research on a given topic; a meta-analysis is a statistical method for combining the results of several studies.
What Did the Researchers Do and Find?
The researchers identified 83 studies that investigated the association between CRP levels measured in people with coronary artery disease and subsequent cardiovascular events. Their examination of these studies revealed numerous reporting and publication short-comings. For example, none of the studies reported a prespecified statistical analysis protocol, yet analyses should be prespecified to avoid the choice of analytical method biasing the study's results. Furthermore, on average, the studies only reported seven of the 17 recommended items in the REMARK reporting guidelines, which were designed to improve the reporting quality of tumor biomarker prognostic studies. The meta-analysis revealed that patients with a CRP level in the top third of the distribution were nearly twice as likely to have a cardiovascular event as patients with a CRP in the bottom third of the distribution (a relative risk of 1.97). However, the outcomes varied considerably between studies (heterogeneity) and there was strong evidence for publication bias—most published studies were small and smaller studies were more likely to report higher relative risks. Adjustment for publication bias reduced the relative risk associated with high CRP levels to 1.19. Finally, nearly all the studies failed to calculate whether CRP measurements discriminated between patients likely and unlikely to have a subsequent cardiovascular event.
What Do These Findings Mean?
These findings suggest that, because of multiple types of reporting and publication bias, the size of the association between CRP levels and prognosis among patients with stable coronary artery disease is extremely uncertain. They also suggest that CRP measurements are unlikely to add anything to the prognostic discrimination achieved by considering blood pressure and other standard clinical factors among this patient group. Thus, the researchers suggest, the recommendation that CRP measurements should be used in the management of patients with stable coronary artery disease ought to be removed from clinical practice guidelines. More generally, these findings increase concerns about the quality of research into prognostic biomarkers and highlight areas that need to be changed, the most fundamental of which is the need to preregister studies on prognostic biomarkers and their analytic protocols.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000286.
The MedlinePlus Encyclopedia has pages on coronary artery disease and C-reactive protein (in English and Spanish)
MedlinePlus provides links to other sources of information on heart disease
The American Heart Association provides information for patients and caregivers on all aspects of cardiovascular disease, including information on the role of C-reactive protein in heart disease
Information is available from the British Heart Foundation on heart disease and keeping the heart healthy
Wikipedia has pages on biomarkers and on C-reactive protein (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
The EQUATOR network is a resource center for good reporting of health research studies
doi:10.1371/journal.pmed.1000286
PMCID: PMC2879408  PMID: 20532236
21.  The association between C-reactive protein and the likelihood of progression to joint replacement in people with rheumatoid arthritis: a retrospective observational study 
Background
This study sought to evaluate the association between systemic inflammation as measured by C-reactive protein and total joint replacement and the association between change in CRP status (low, ≤ 10 mg/L and high, >10 mg/L) measured over one year and total joint replacement in patients diagnosed with rheumatoid arthritis.
Methods
A cohort of patients was selected from The Health Improvement Network (THIN) dataset of anonymised patient-level data from UK general practice with a confirmed chronic rheumatic diagnosis. Surgery-free survival was evaluated using Cox proportional hazards regression models (CPHM).
Results
2,421 cases had at least one CRP measurement of which 125 cases (5.2%) had at least one major joint replacement. In CPHM, each additional unit increase in log mean CRP (range 1 to 6) was associated with a hazard ratio (HR) for major orthopaedic surgery of 1.36 (95% CI 1.10 to 1.67; p = 0.004), after controlling for age at first rheumatoid presentation and average body mass index over the same observation period. Repeated CRP observations around one year apart were recorded in 1,314 subjects. After controlling for confounding factors, in cases whose CRP remained high (>10 mg/L), the HR for joint replacement increased more than two-fold (p = 0.040) relative to cases whose CRP remained low. In patients whose CRP increased from low to high, the HR was 1.86 compared to those who remained in a low state (p = 0.217). By comparison, among those subjects whose CRP was reduced from a high to low state, the hazard ratio was more than halved (1.46) from to those who remained high (p = 0.441). Although underpowered, the trend evident from CRP change corroborates the association of TJR progression with mean CRP.
Conclusion
CRP level predicts progression to major joint replacement after standardisation for relevant risk factors as did change in CRP status between low and high states observed over one year.
doi:10.1186/1471-2474-9-146
PMCID: PMC2585569  PMID: 18983663
22.  Platelet Count Measured Prior to Cancer Development Is a Risk Factor for Future Symptomatic Venous Thromboembolism: The Tromsø Study 
PLoS ONE  2014;9(3):e92011.
Background
Elevated platelet count is associated with risk of venous thromboembolism in cancer patients initiating chemotherapy. It is not known whether this risk by platelet count is causal or merely reflects the malignant disease. We investigated whether pre-cancer platelet count alone or together with high leukocyte count was associated with risk of venous thromboembolism in subjects who did and did not develop cancer during follow-up in a population-based cohort study.
Methods
Platelet count and other baseline characteristics were measured in 25160 initially cancer-free subjects who participated in the Tromsø Study in 1994–1995. Incident cancer and symptomatic venous thromboembolism events were registered up to December 31st, 2009. Multivariable Cox regression models were used to calculate hazard ratio for venous thromboembolism across categories of platelet count (<40th, 40–80th, and >80th percentile) with 95% confidence interval.
Results
During follow-up, 2082 subjects were diagnosed with cancer. Platelet count was measured on average 8.3 years before the cancer diagnosis. There were 129 venous thromboembolism events in the cancer cohort (13.5 per 1000 person-years) and 377 in the non-cancer cohort (1.2 per 1000 person-years). In cancer patients, pre-cancer platelet count above the 80th percentile (≥295×109/L) was associated with a 2-fold higher risk of venous thromboembolism (Hazard ratio: 1.98, 95% confidence interval 1.21–3.23) compared to platelet count below the 40th percentile (<235×109/L). Concomitant high platelet and leukocyte counts showed a synergistic effect on the VTE risk. In cancer-free subjects, no association was found.
Comment
In conclusion, pre-cancer platelet count was associated with risk of symptomatic venous thromboembolism in cancer patients, but not in cancer-free subjects. Our findings suggest that platelet count and platelet-leukocyte interactions may play a role in the pathogenesis of cancer-related venous thromboembolism.
doi:10.1371/journal.pone.0092011
PMCID: PMC3958406  PMID: 24642868
23.  Effects of Smoking Intensity and Cessation on Inflammatory Markers in a Large Cohort of Active Smokers 
American heart journal  2010;160(3):458-463.
Background
Cigarette smoking has been associated with increases in C-reactive protein (CRP) and leukocyte counts (WBC); however, the effects of smoking intensity and smoking cessation on inflammatory markers have not been evaluated prospectively in a large, modern cohort of current smokers.
Methods
WBC count and high-sensitivity CRP were measured in current smokers enrolled in a randomized, prospective clinical trial of five smoking cessation pharmacotherapies. Smoking intensity parameters included: cigarettes/day, pack-years, Fagerstrom Test of Nicotine Dependence (FTND) score, and carbon monoxide (CO) levels. CRP also was measured after 1 year with assessment of abstinence status.
Results
The 1,504 current smokers (58% female) were mean (standard deviation): 44.7 (11.1) years old, smoked 21.4 (8.9) cigarettes/day and had a smoking burden of 29.4 (20.4) pack-years. Log (CRP) was not associated with any marker of smoking intensity, except for a weak correlation with pack-years (r=0.05, p=0.047). In contrast, statistically significant correlations were observed between all 4 markers of smoking intensity and WBC count (all p≤0.011). In multivariable models, waist circumference (p<0.001) and triglycerides (p<0.05), but no markers of smoking intensity, were associated with log(CRP). However, pack-years (p=0.002), cigarettes/day (p=0.013), CO (p<0.001), and FTND (p<0.001) were independently associated with WBC count. After 1 year, log(CRP) (p=0.296) and changes in log(CRP) (p=0.455) did not differ between abstainers and continuing smokers.
Conclusions
Smoking intensity is associated with increased WBC count, but not CRP levels. Smoking cessation does not reduce CRP. The relationship between CRP and smoking intensity may be masked by CRP’s stronger relationship with adiposity.
doi:10.1016/j.ahj.2010.06.006
PMCID: PMC2937015  PMID: 20826253
C-reactive protein; Inflammation; Leukocytes; Risk factors; Smoking
24.  C - Reactive Protein, Inflammatory Conditions and Cardiovascular Disease Risk 
The American journal of medicine  2007;120(12):1054-1062.
Background
It is uncertain to what extent high C-reactive protein (CRP) concentrations reflect the presence of inflammatory conditions in the community.
Methods
We evaluated 3782 Framingham participants (mean age 55 years; 52% women) free of baseline cardiovascular disease. Logistic regression models examined the prevalence of common inflammatory conditions by CRP categories whereas a separate matched case-referent analysis evaluated the prevalence of uncommon inflammatory conditions. Cox models were used to assess the influence of common inflammatory conditions on relations between CRP and incident cardiovascular disease.
Results
Common inflammatory conditions were reported by nearly half of the participants; these individuals were more likely to have markedly-high CRP concentrations (>10mg/L, P for trend=0.001). In multivariable models, there were increased odds of having at least one common inflammatory condition with CRP concentrations of 1–3.0, 3.01–10, and >10mg/L, compared to the referent category (<1mg/L); the respective odds ratios with 95% confidence intervals were 1.41 (1.07–1.86), 1.45 (1.07–2.98) and 1.64 (1.09–2.47) in men, and 1.08 (0.82–1.43), 1.07 (0.80–1.44) and 1.38 (0.97–1.96) in women. In case-referent analyses, uncommon inflammatory conditions were more common in individuals with CRP >10mg/L compared to those with CRP <1mg/L (12.1% versus 6.6%; P=0.0001). In multivariable models, higher CRP categories were not associated with incident cardiovascular disease, and with additional adjustment for inflammatory conditions, results remained unchanged.
Conclusion
There is high prevalence of common and uncommon inflammatory conditions in individuals with high CRP concentrations. Higher CRP concentrations should be interpreted with caution in cardiovascular disease risk assessment.
doi:10.1016/j.amjmed.2007.08.037
PMCID: PMC2215387  PMID: 18060926
C-reactive protein; Inflammation; Arthritis; Cardiovascular Disease; Cohort Study
25.  Genetic Loci Influencing C-reactive Protein Levels and Risk of Coronary Heart Disease 
Context:
Plasma levels of C-reactive protein (CRP) are independently associated with risk of coronary heart disease, but whether CRP is causally associated with coronary heart disease or merely a marker of underlying atherosclerosis is uncertain.
Objective:
To investigate association of genetic loci with CRP levels and risk of coronary heart disease.
Design, setting and participants:
We first carried out a genome-wide association (n=17,967) and replication study (n=14,747) to identify genetic loci associated with plasma CRP concentrations. Data collection took place between 1989 and 2008 and genotyping between 2003 and 2008. We carried out a Mendelian randomisation study of the most closely associated SNP in the CRP locus and published data on other CRP variants involving a total of 28,112 cases and 100,823 controls, to investigate the association of CRP variants with coronary heart disease. We compared our finding with that predicted from meta-analysis of observational studies of CRP levels and risk of coronary heart disease. For the other loci associated with CRP levels, we selected the most closely associated SNP for testing against coronary heart disease among 14,365 cases and 32,069 controls.
Main outcome measure:
Risk of coronary heart disease.
Results:
Polymorphisms in five genetic loci were strongly associated with CRP levels (% difference per minor allele): SNP rs6700896 in LEPR (−14.7% [95% Confidence Interval {CI}], −17.5 – −11.9, P=1.6×10−21), rs4537545 in IL6R (−10.8% [95% CI, −13.8 – −7.7], P=5.1×10−11), rs7553007 in CRP locus (−20.7% [95% CI, −23.5 – −17.9], P=3.3×10−38), rs1183910 in HNF1A (−13.6% [95% CI, −16.4 – −10.6], P=1.2×10−17) and rs4420638 in APOE-CI-CII (−21.8% [95% CI, −25.4 – −18.1], P=2.1×10−25). Association of SNP rs7553007 in the CRP locus with coronary heart disease gave odds ratio (OR) 0.98 (95% CI, 0.94 – 1.01) per 20% lower CRP. Our Mendelian randomisation study of variants in the CRP locus showed no association with coronary heart disease: OR 1.00 (95% CI, 0.97 – 1.02) per 20% lower CRP, compared with OR 0.94 (95% CI, 0.94 – 0.95) predicted from meta-analysis of the observational studies of CRP levels and coronary heart disease (Z-score −3.45, P<.001). SNPs rs6700896 in LEPR (OR 1.06 [95% CI, 1.02 – 1.09] per minor allele), rs4537545 in IL6R (OR 0.94 [95% CI, 0.91 – 0.97]) and rs4420638 in the APOE-CI-CII cluster (OR 1.16 [95% CI, 1.12 – 1.21]) were all associated with risk of coronary heart disease.
Conclusions:
The lack of concordance between the effect on coronary heart disease risk of CRP genotypes and CRP levels argues against a causal association of CRP with coronary heart disease.
doi:10.1001/jama.2009.954
PMCID: PMC2803020  PMID: 19567438

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