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1.  Abnormal Pap tests and human papillomavirus infections among HIV infected and uninfected women who have sex with women 
Objective
To estimate the frequency of abnormal Pap and human papillomavirus (HPV) positivity among HIV seropositive and seronegative women who have sex with women (WSW).
Methods
Pap and HPV DNA PCR tests were obtained every six months from women in a U.S. cohort of HIV seropositive and seronegative women. WSW were women reporting no male and at least one female sex partner over five years. WSW were frequency matched 1:5 to women reporting sex only with men (WSM) and assessed using multivariable generalized estimating equation logistic regression models.
Results
Paps at study entry were abnormal in 12 (21%) of 49 HIV seropositive WSW, 151 (64%) of 245 HIV seropositive WSM, 3 (9%) of 24 HIV seronegative WSW, and 16 (11%) of 120 seronegative WSM. HPV was found at entry in 18 (42%) HIV seropositive WSW, 109 (52%) HIV seropositive WSM, 6 (27%) HIV seronegative WSW and 13 (13%) HIV seronegative WSM. After controlling for HIV serostatus and CD4 count, WSW had marginally lower odds than WSM of Pap abnormality (O.R. 0.59, 95% C.I. 0.33, 1.03) and of HPV (O.R. 0.53, 95% C.I. 0.32, 0.89). After controlling for partner gender, HIV seropositivity and lower CD4 count were associated with any HPV, oncogenic HPV, any abnormal Pap result, and HSIL or worse (P < 0.0001 for all).
Conclusion
While risks for abnormal Pap and HPV are modestly lower in WSW than WSM, both are common in HIV seropositive women regardless of sexual preference. WSW and WSM should be screened similarly.
doi:10.1097/LGT.0b013e3182942733
PMCID: PMC3905442  PMID: 23959300
Human papillomavirus; HIV in women; women who have sex with women
2.  Metformin Use and Endometrial Cancer Survival 
Gynecologic oncology  2013;132(1):236-240.
Objective
Impaired glucose tolerance and diabetes are risk factors for the development of uterine cancer. Although greater progression free survival among diabetic patients with ovarian and breast cancer using metformin have been reported, no studies have assessed the association of metformin use with survival in women with endometrial cancer (EC).
Methods
We conducted a single-institution retrospective cohort study of all patients treated for uterine cancer from January 1999 through December 2009. Demographic, medical, social, and survival data were abstracted from medical records and the national death registry. Overall survival (OS) was estimated using Kaplan-Meier methods. Cox models were utilized for multivariate analysis. All statistical tests were two-sided.
Results
Of 985 patients, 114 (12%) had diabetes and were treated with metformin, 136 (14%) were diabetic but did not use metformin, and 735 (74%) had not been diagnosed with diabetes. Greater OS was observed in diabetics with non-endometrioid EC who used metformin than in diabetic cases not using metformin and non-endometrioid EC cases without diabetes (log rank test (p=0.02)). This association remained significant (hazard ratio = 0.54, 95% CI: 0.30–0.97, p<0.04) after adjusting for age, clinical stage, grade, chemotherapy treatment, radiation treatment and presence of hyperlipidemia in multivariate analysis. No association between metformin use and OS in diabetics with endometrioid histology was observed.
Conclusion
Diabetic EC patients with non-endometrioid tumors who used metformin had lower risk of death than women with EC who did not use metformin. These data suggest that metformin might be useful as adjuvant therapy for non-endometrioid EC.
doi:10.1016/j.ygyno.2013.10.026
PMCID: PMC3904540  PMID: 24189334
Metformin; endometrial cancer; non-endometrioid; adjuvant therapy; retrospective cohort study
3.  Insulin, Insulin-like Growth Factor-I, Endogenous Estradiol, and Risk of Colorectal Cancer in Postmenopausal Women 
Cancer research  2008;68(1):329-337.
Obesity is a risk factor for colorectal cancer, and hyperinsulinemia, a common condition in obese patients, may underlie this relationship. Insulin, in addition to its metabolic effects, has promitotic and antiapoptotic activity that may be tumorigenic. Insulin-like growth factor (IGF)-I, a related hormone, shares sequence homology with insulin, and has even stronger mitogenic effects. However, few prospective colorectal cancer studies directly measured fasting insulin, and none evaluated free IGF-I, or endogenous estradiol, a potential cofactor in postmenopausal women. Therefore, we conducted a case-cohort investigation of colorectal cancer among nondiabetic subjects enrolled in the Women’s Health Initiative Observational Study, a prospective cohort of 93,676 postmenopausal women. Fasting baseline serum specimens from all incident colorectal cancer cases (n = 438) and a random subcohort (n = 816) of Women’s Health Initiative Observational Study subjects were tested for insulin, glucose, total IGF-I, free IGF-I, IGF binding protein-3, and estradiol. Comparing extreme quartiles, insulin [hazard ratio (HR)q4–q1, 1.73; 95% confidence interval (CI), 1.16–2.57; ptrend = 0.005], waist circumference (HRq4–q1, 1.82; 95% CI, 1.22–2.70; ptrend = 0.001), and free IGF-I (HRq4–q1, 1.35; 95% CI, 0.92–1.98; Ptrend = 0.05) were each associated with colorectal cancer incidence in multivariate models. However, these associations each became nonsignificant when adjusted for one another. Endogenous estradiol levels, in contrast, were positively associated with risk of colorectal cancer (HR comparing high versus low levels, 1.53; 95% CI, 1.05–2.22), even after control for insulin, free IGF-I, and waist circumference. These data suggest the existence of at least two independent biological pathways that are related to colorectal cancer: one that involves endogenous estradiol, and a second pathway broadly associated with obesity, hyperinsulinemia, and free IGF-I.
doi:10.1158/0008-5472.CAN-07-2946
PMCID: PMC4225702  PMID: 18172327
5.  Insulin-Like Growth Factor Axis and Risk of Type 2 Diabetes in Women 
Diabetes  2012;61(9):2248-2254.
IGF-I shares structural homology and in vitro metabolic activity with insulin. Laboratory models suggest that IGF-I and its binding proteins IGFBP-1 and IGFBP-2 have potentially beneficial effects on diabetes risk, whereas IGFBP-3 may have adverse effects. We therefore conducted a prospective nested case-control investigation of incident diabetes (n = 742 case subjects matched 1:1 to control subjects) and its associations with IGF-axis protein levels in the Nurses’ Health Study, a cohort of middle-aged women. The median time to diabetes was 9 years. Statistical analyses were adjusted for multiple risk factors, including insulin and C-reactive protein. Diabetes risk was fivefold lower among women with baseline IGFBP-2 levels in the top versus bottom quintile (odds ratio [OR]q5–q1 = 0.17 [95% CI 0.08–0.35]; P trend < 0.0001) and was also negatively associated with IGFBP-1 levels (ORq5–q1 = 0.37 [0.18–0.73]; P trend = 0.0009). IGFBP-3 was positively associated with diabetes (ORq5–q1 = 2.05 [1.20–3.51]; P trend = 0.002). Diabetes was not associated with total IGF-I levels, but free IGF-I and diabetes had a significant association that varied (P interaction = 0.003) by insulin levels above the median (ORq5–q1 = 0.48 [0.26–0.90]; P trend = 0.0001) versus below the median (ORq5–q1 = 2.52 [1.05–6.06]; P trend < 0.05). Thus, this prospective study found strong associations of incident diabetes with baseline levels of three IGFBPs and free IGF-I, consistent with hypotheses that the IGF axis might influence diabetes risk.
doi:10.2337/db11-1488
PMCID: PMC3425426  PMID: 22554827
6.  The role of insulin-like growth factor-I and its binding proteins in glucose homeostasis and type 2 diabetes 
Summary
This review addresses the possible role of the insulin-like growth factor (IGF)-axis in normal glucose homoeostasis and in the etiopathogenesis of type 2 diabetes. IGF-I, a peptide hormone, shares amino acid sequence homology with insulin and has insulin-like activity; most notably, the promotion of glucose uptake by peripheral tissues. Type 2 diabetes as well as pre-diabetic states, including impaired fasting glucose and impaired glucose tolerance, are associated cross-sectionally with altered circulating levels of IGF-I and its binding proteins (IGFBPs). Administration of recombinant human IGF-I has been reported to improve insulin sensitivity in healthy individuals as well as in patients with insulin resistance and type 2 diabetes. Further, IGF-I may have beneficial effects on systemic inflammation, a risk factor for type 2 diabetes, and on pancreatic β-cell mass and function. There is considerable inter-individual heterogeneity in endogenous levels of IGF-I and its binding proteins; however, the relationship between these variations and the risk of developing type 2 diabetes has not been extensively investigated. Large prospective studies are required to evaluate this association.
doi:10.1002/dmrr.919
PMCID: PMC4153414  PMID: 19145587
insulin-like growth factor (IGF)-I; glucose; diabetes; IGFBP
7.  Concomitant anal and cervical human papillomavirusV infections and intraepithelial neoplasia in HIV-infected and uninfected women 
AIDS (London, England)  2013;27(11):1743-1751.
Objective
To assess factors associated with concomitant anal and cervical human papillomavirus (HPV) infections in HIV-infected and at-risk women.
Design
A study nested within the Women’s Interagency HIV Study (WIHS), a multi-center longitudinal study of HIV-1 infection in women conducted in six centers within the United States.
Methods
Four hundred and seventy HIV-infected and 185 HIV-uninfected WIHS participants were interviewed and examined with anal and cervical cytology testing. Exfoliated cervical and anal specimens were assessed for HPV using PCR and type-specific HPV testing. Women with abnormal cytologic results had colposcopy or anoscopy-guided biopsy of visible lesions. Logistic regression analyses were performed and odds ratios (ORs) measured the association for concomitant anal and cervical HPV infection.
Results
One hundred and sixty-three (42%) HIV-infected women had detectable anal and cervical HPV infection compared with 12 (8%) of the HIV-uninfected women (P <0.001). HIV-infected women were more likely to have the same human papillomavirus (HPV) genotype in the anus and cervix than HIV-uninfected women (18 vs. 3%, P <0.001). This was true for both oncogenic (9 vs. 2%, P = 0.003) and nononcogenic (12 vs. 1%, P <0.001) HPV types. In multivariable analysis, the strongest factor associated with both oncogenic and nononcogenic concomitant HPV infection was being HIV-infected (OR = 4.6 and OR = 16.9, respectively). In multivariable analysis of HIV-infected women, CD4+ cell count of less than 200 was the strongest factor associated with concomitant oncogenic (OR = 4.2) and nononcogenic (OR = 16.5) HPV infection.
Conclusion
HIV-infected women, particularly those women with low CD4+ cell counts, may be good candidates for HPV screening and monitoring for both cervical and anal disease
doi:10.1097/QAD.0b013e3283601b09
PMCID: PMC3917497  PMID: 23803793
anal intraepithelial neoplasia; cervical intraepithelial neoplasia; HIV-infection; human papillomavirus; women
8.  Circulating Soluble Cytokine Receptors and Colorectal Cancer Risk 
Background
Soluble cytokine receptors and receptor antagonist of proinflammatory cytokines can modify cytokine signaling and may affect cancer risk.
Methods
In a case-cohort study nested within the Women’s Health Initiative cohort of postmenopausal women, we assessed the associations of plasma levels of IL-1 receptor antagonist (IL-1Ra) and the soluble receptors of IL-1 (sIL-1R2), IL-6 (sIL-6R and sgp130), and TNF (sTNFR1 and sTNFR2) with risk of colorectal cancer in 433 cases and 821 subcohort subjects. Baseline levels of estradiol, insulin, leptin, IL-6, and TNF-α measured previously were also available for data analysis.
Results
After adjusting for significant covariates – including age, race, smoking, colonoscopy history, waist circumference, and levels of estrogen, insulin, and leptin – relatively high levels of sIL-6R and sIL-1R2 were associated with reduced colorectal cancer risk [hazard ratios comparing extreme quartiles (HRQ4-Q1) for sIL-6R = 0.56, 95% CI = 0.38–0.83; HRQ4-Q1 for sIL-1R2 = 0.44, 95% CI = 0.29–0.67]. The associations with IL-1Ra, sgp130, sTNFR1, and sTNFR2 were null. The inverse association of sIL-1R2 with colorectal cancer risk persisted in cases diagnosed ≤5 and >5 years from baseline blood draw; the association with sIL-6R, however, was not evident in the latter group, possibly indicating that relatively low levels of sIL-6R in cases might be due to undiagnosed cancer at the time of blood draw.
Conclusions
High circulating levels of sIL-1R2 may be protective against colorectal carcinogenesis and/or be a marker of reduced risk for the disease.
Impact
sIL-1R2 has potential to be a chemopreventive and/or immunotherapeutic agent in inflammation-related diseases.
doi:10.1158/1055-9965.EPI-13-0545
PMCID: PMC3947182  PMID: 24192010
soluble cytokine receptor; receptor antagonist; colorectal cancer; IL-1; IL-6; TNF
9.  Resistin, but not Adiponectin and Leptin, is Associated with the Risk of Ischemic Stroke Among Postmenopausal Women: Results from the Women’s Health Initiative 
Background
Adipose tissue is considered an endocrine organ that secretes adipokines which possibly mediate the effects of obesity on risk of cardiovascular disease. However, there are yet limited prospective data on the association between circulating adipokine levels and risk of ischemic stroke. We aimed to examine the associations of three adipokines (adiponectin, leptin and resistin) with risk of ischemic stroke.
Methods and Results
We conducted a prospective nested case-control study (972 stroke cases and 972 matched controls) within the Women’s Health Initiative Observational Study cohort. The controls were matched to cases on age, race/ethnicity, date of study enrollment and follow-up time. Adipokine levels were associated with established stroke risk factors, such as obesity and systolic blood pressure. Adjusted for body mass index, the odds ratios (OR) for incident ischemic stroke comparing the highest (Q4) to the lowest quartile (Q1) were 0.81 (95% confidence intervals [CI]: 0.61–1.08; p-trend: 0.068) for adiponectin, 1.15 (95% CI: 0.83–1.59; p-trend: 0.523) for leptin, and 1.57 (95% CI: 1.18–2.08; p-trend: 0.002) for resistin. The association for resistin remained significant even after accounting for established stroke risk factors (OR: 1.39; 95% CI: 1.01–1.90; p-trend: 0.036). Further adjustment for markers for inflammation, angiogenesis, and endothelial function also did not affect our results.
Conclusions
Circulating levels of resistin, but not those of adiponectin or leptin, are associated with an increased risk of incident ischemic stroke in postmenopausal women, independent of obesity and other CVD risk factors.
doi:10.1161/STROKEAHA.110.607853
PMCID: PMC4059356  PMID: 21546486
stroke; adipokines; women
10.  The insulin-like growth factor axis and risk of liver disease in hepatitis C virus/HIV-co-infected women 
AIDS (London, England)  2008;22(4):527-531.
Objective
Insulin-like growth factor (IGF) I stimulates the proliferation of hepatic stellate cells (HSC), the primary source of extracellular matrix accumulation in liver fibrosis. In contrast, insulin-like growth factor binding protein (IGFBP) 3, the most abundant IGFBP in circulation, negatively modulates HSC mitogenesis. To investigate the role of the IGF axis in hepatitis C virus (HCV)-related liver disease among high-risk patients, we prospectively evaluated HCV-viremic/HIV-positive women.
Design
A cohort investigation.
Methods
Total IGF-I and IGFBP-3 were measured in baseline serum specimens obtained from 472 HCV-viremic/HIV-positive subjects enrolled in the Women's Inter-agency HIV Study, a large multi-institutional cohort. The aspartate aminotransferase to platelet ratio index (APRI), a marker of liver fibrosis, was assessed annually.
Results
Normal APRI levels (< 1.0) at baseline were detected in 374 of the 472 HCV-viremic/HIV-positive subjects tested, of whom 302 had complete liver function test data and were studied. IGF-I was positively associated [adjusted odds ratio comparing the highest and lowest quartiles (AORq4–q1), 5.83; 95% confidence interval (CI) 1.17–29.1; Ptrend = 0.03], and IGFBP-3 was inversely associated (AORq4–q1, 0.13; 95% CI 0.02–0.76; Ptrend = 0.04), with subsequent (incident) detection of an elevated APRI level(> 1.5), after adjustment for the CD4 T-cell count, alcohol consumption, and other risk factors.
Conclusion
High IGF-I may be associated with increased risk and high IGFBP-3 with reduced risk of liver disease among HCV-viremic/HIV-positive women.
doi:10.1097/QAD.0b013e3282f22cdf
PMCID: PMC3507535  PMID: 18301066
aspartate aminotransferase to platelet ratio index; APRI; hepatitis C virus (HCV); HIV; IGFBP-3; IGF; liver disease
11.  Invasive cervical cancer risk among HIV-infected women: A North American multi-cohort collaboration prospective study 
Objective
HIV infection and low CD4+ T-cell count are associated with an increased risk of persistent oncogenic HPV infection – the major risk factor for cervical cancer. Few reported prospective cohort studies have characterized the incidence of invasive cervical cancer (ICC) in HIV-infected women.
Methods
Data were obtained from HIV-infected and -uninfected female participants in the NA-ACCORD with no history of ICC at enrollment. Participants were followed from study entry or January, 1996 through ICC, loss-to follow-up or December, 2010. The relationship of HIV infection and CD4+ T-cell count with risk of ICC was assessed using age-adjusted Poisson regression models and standardized incidence ratios (SIR). All cases were confirmed by cancer registry records and/or pathology reports. Cervical cytology screening history was assessed through medical record abstraction.
Results
A total of 13,690 HIV-infected and 12,021 HIV-uninfected women contributed 66,249 and 70,815 person-years (pys) of observation, respectively. Incident ICC was diagnosed in 17 HIV-infected and 4 HIV-uninfected women (incidence rate of 26 and 6 per 100,000 pys, respectively). HIV-infected women with baseline CD4+ T-cells of ≥ 350, 200–349 and <200 cells/uL had a 2.3-times, 3.0-times and 7.7-times increase in ICC incidence, respectively, compared with HIV-uninfected women (Ptrend =0.001). Of the 17 HIV-infected cases, medical records for the 5 years prior to diagnosis showed that 6 had no documented screening, 5 had screening with low grade or normal results, and 6 had high-grade results.
Conclusions
This study found elevated incidence of ICC in HIV-infected compared to -uninfected women, and these rates increased with immunosuppression.
doi:10.1097/QAI.0b013e31828177d7
PMCID: PMC3633634  PMID: 23254153
Human papilloma virus; HIV-infection; Invasive Cervical Cancer; Immunosuppression
12.  Association of HIV clinical disease progression with profiles of early immune activation: results from a cluster analysis approach 
AIDS (London, England)  2013;27(9):1473-1481.
Objective
CD4 and CD8 T-cell activation are independent predictors of AIDS. The complete activation profile of both T-cell subtypes and their predictive value for AIDS risk is largely unknown.
Design
A total of 564 AIDS-free women in the Women's Interagency HIV Study were followed over 6.1 years (median) after T-cell activation assessment. A cluster analysis approach was used to evaluate the concurrent activation patterns of CD4 and CD8 T cells at the beginning of follow-up in relation to AIDS progression.
Methods
Percentages of CD4 and CD8 T cells with HLA-DR± and CD38± were assessed by flowcytometry. Eight immunologic variables (four on each CD4+ and CD8+: DR± and CD38±) were assessed to yield a 4-cluster solution on samples obtained before clinical endpoints. Proportional hazards survival regression estimated relative risks for AIDS progression by cluster membership.
Results
Compared with the other three clusters, outstanding activation features of each distinct cluster of women were: Cluster 1: higher CD8+CD38– DR– (average = 41% of total CD8 T-cell pool), CD4+CD38– DR– (average = 53% of total CD4 T-cell pool), and CD8+CD38– DR+ (28%); Cluster 2: higher CD8+CD38+DR– (44%) and CD4+CD38+DR– (58%); Cluster 3: higher CD8+CD38+DR+ (49%) and CD4+ CD38+DR– (48%); Cluster 4: higher CD8+CD38+DR+ (49%), CD4+CD38+DR+ (36%) and CD4+CD38– DR+ (19%). Compared with cluster 1, women in cluster 4 had two-fold increased risk of AIDS progression (Hazard ratio = 2.13; 95% confidence interval = 1.30–3.50) adjusted for CD4 cell count, HIV RNA, and other confounders.
Conclusion
A profile including CD4 and CD8 T-cell activation provided insight into HIV pathogenesis indicating concurrent hyperactivation of CD4 and CD8 T cells is associated with AIDS progression.
doi:10.1097/QAD.0b013e3283601bad
PMCID: PMC3949252  PMID: 23945505
AIDS; cluster analysis; immune activation
14.  Hepatocyte Growth Factor and the Risk of Developing Ischemic Stroke Among Postmenopausal Women: Results from the Women’s Health Initiative 
Background
Hepatocyte growth factor (HGF) is a potent angiogenic factor and may play a role in the development and progression of atherosclerotic lesions, the underlying mechanism of cardiovascular disease. However, there have been no prospective studies examining the relationship between HGF levels and risk of stroke.
Methods and Results
We conducted a nested case-control study (972 incident stroke cases and 1:1 age- and race-matched controls) to prospectively evaluate the association between plasma HGF and risk of ischemic stroke within the Women’s Health Initiative Observational Study, a cohort of postmenopausal women aged 50–79 years. Baseline HGF levels were correlated positively with body mass index (BMI), systolic blood pressure, low-density lipoprotein cholesterol, insulin resistance, and inflammatory markers such as C-reactive protein, and inversely with high-density lipoprotein cholesterol (all P-values <0.05). Baseline HGF levels were higher among cases than controls (geometric means 601.8 vs. 523.2 pg/mL, p = 0.003). Furthermore, the risk of incident ischemic stroke was significantly greater amongst women in the highest versus lowest quartile of plasma HGF levels (odds ratio [OR] = 1.46; 95% confidence interval [CI]: 1.12–1.91; Ptrend = 0.003), in a conditional logistic regression model that adjusted for BMI. These results were only slightly attenuated after further adjustment for additional stroke risk factors (OR=1.39; 95% CI=1.04–1.85, Ptrend=0.023).
Conclusions
Circulating levels of HGF are associated with an increased risk of incident ischemic stroke, independent of obesity and other risk factors for cardiovascular disease among postmenopausal women aged 50–79 years.
doi:10.1161/STROKEAHA.109.567719
PMCID: PMC3903044  PMID: 20203323
Hepatocyte growth factor; ischemic stroke; women
15.  Associations of Insulin-Like Growth Factor (IGF)–I and IGF-Binding Protein–3 with HIV Disease Progression in Women 
The Journal of infectious diseases  2008;197(2):319-327.
Background
The insulin-like growth factor (IGF) axis has been hypothesized to influence the rate of human immunodeficiency virus (HIV) disease progression. This premise is based largely on laboratory models showing that IGF-I stimulates thymic growth and increases lymphocyte numbers and that IGF-binding protein (IGFBP)–3 has an opposing effect, inhibiting hematopoietic stem cell development.
Methods
We studied 1422 HIV-infected women enrolled in a large cohort that entailed semiannual follow-up (initiated in 1994). Baseline serum samples were tested for IGF-I and IGFBP-3 to determine their associations with incident clinical acquired immunodeficiency syndrome (AIDS) and CD4+ T cell count decline prior to April 1996 (before the era of highly active antiretroviral therapy [HAART]).
Results
Low IGF-I levels (Ptrend = .02) and high IGFBP-3 levels (Ptrend = .02) were associated with rapid CD4+ T cell count decline. Only IGFBP-3, however, was significantly associated with AIDS incidence (hazard ratio for highest vs. lowest quartile, 2.65 [95% confidence interval, 1.30–5.42]; Ptrend = .02) in multivariable models.
Conclusions
These findings suggest that serum levels of IGFBP-3 (and possibly IGF-I) are associated with the rate of HIV disease progression in women and, more broadly, that interindividual heterogeneity in the IGF axis may influence HIV pathogenesis. If correct, the IGF axis could be a target for interventions to slow HIV disease progression and extend the time before use of HAART becomes necessary.
doi:10.1086/524848
PMCID: PMC3127259  PMID: 18177247
16.  Relation of HLA Class I and II Supertypes with Spontaneous Clearance of Hepatitis C Virus 
Genes and immunity  2013;14(5):330-335.
Human leukocyte antigen (HLA) genotype has been associated with probability of spontaneous clearance of hepatitis C virus (HCV). However, no prior studies have examined whether this relationship may be further characterized by grouping HLA alleles according to their supertypes, defined by their binding capacities. There is debate regarding the most appropriate method to define supertypes. Therefore, previously reported HLA supertypes (46 class I and 25 class II) were assessed for their relation with HCV clearance in a population of 758 HCV-seropositive women. Two HLA class II supertypes were significant in multivariable models that included: (i) supertypes with significant or borderline associations with HCV clearance after adjustment for multiple tests, and (ii) individual HLA alleles not part of these supertypes, but associated with HCV clearance in our prior study in this population. Specifically, supertype DRB3 (prevalence ratio (PR)=0.4; p=0.004) was associated with HCV persistence while DR8 (PR=1.8; p=0.01) was associated with HCV clearance. Two individual alleles (B*57:01 and C*01:02) associated with HCV clearance in our prior study became non-significant in analysis that included supertypes while B*57:03 (PR=1.9; p=0.008) and DRB1*07:01 (PR=1.7; p=0.005) retained significance. These data provide epidemiologic support for the significance of HLA supertypes in relation to HCV clearance.
doi:10.1038/gene.2013.25
PMCID: PMC3723800  PMID: 23636221
hepatitis C virus; HLA; human leukocyte antigen; supertype
17.  Estimation and inference on correlations between biomarkers with repeated measures and left-censoring due to minimum detection levels 
Statistics in medicine  2012;31(21):10.1002/sim.5371.
Statistical approaches for estimating and drawing inference on the correlation between two biomarkers which are repeatedly assessed over time and subject to left-censoring due to minimum detection levels are lacking. We propose a linear mixed-effects model and estimate the parameters with the Monte Carlo Expectation Maximization (MCEM) method. Inferences regarding the model parameters and the correlation between the biomarkers are performed by applying Louis’s method and the delta method. Simulation studies were conducted to compare the proposed MCEM method with existing methods including the MLE method, the multiple imputation (MI) method, and two widely used ad hoc approaches: replacing the censored values with the detection limit (DL) or with half of the detection limit (HDL). The results show that the performance of the MCEM with respect to relative bias and coverage probability for the 95% confidence interval is superior to the DL and HDL approaches and exceeds that of the MI method at medium to high levels of censoring, and the standard error estimates from the MCEM method are close to ideal. The MLE method can estimate the parameters accurately; however, a non-positive definite information matrix can occur so that the variances are not estimable. These five methods are illustrated with data from a longitudinal HIV study to estimate and draw inference on the correlation between HIV RNA levels measured in plasma and in cervical secretions at multiple time points.
doi:10.1002/sim.5371
PMCID: PMC3875381  PMID: 22714546
information matrix; longitudinal data; mixed-effects; monte carlo expectation maximization
18.  Quantifying Mediating Effects of Endogenous Estrogen and Insulin in the Relation between Obesity, Alcohol Consumption, and Breast Cancer 
Background
Increased exposure to endogenous estrogen and/or insulin may partly explain the relationship of obesity, physical inactivity, and alcohol consumption and postmenopausal breast cancer. However, these potential mediating effects have not been formally quantified in a survival analysis setting.
Methods
We combined data from two case–cohort studies based in the Women’s Health Initiative- Observational Study with serum estradiol levels, one of which also had insulin levels. A total of 1,601 women (601 cases) aged 50 to 79 years who were not using hormone therapy at enrollment were included. Mediating effects were estimated by applying a new method based on the additive hazard model.
Results
A five-unit increase in body mass index (BMI) was associated with 50.0 [95% confidence interval (CI), 23.2–76.6] extra cases per 100,000 women at-risk per year. Of these, 23.8% (95% CI, 2.9–68.4) could be attributed to estradiol and 65.8% (95% CI, 13.6–273.3) through insulin pathways. The mediating effect of estradiol was greater (48.8%; 95% CI, 18.8–161.1) for BMI when restricted to estrogen receptor positive (ER+) cases. Consuming 7+ drinks/wk compared with abstinence was associated with 164.9 (95% CI, 45.8–284.9) breast cancer cases per 100,000, but no significant contribution from estradiol was found. The effect of alcohol on breast cancer was restricted to ER+ breast cancers.
Conclusions
The relation of BMI with breast cancer was partly mediated through estradiol and, to a greater extent, through insulin.
Impact
The findings provide support for evaluation of interventions to lower insulin and estrogen levels in overweight and obese postmenopausal women to reduce breast cancer risk.
doi:10.1158/1055-9965.EPI-12-0310
PMCID: PMC3858186  PMID: 22564867
19.  Genital Warts and Vulvar Intraepithelial Neoplasia: Natural History and Effects of Treatment and Human Immunodeficiency Virus Infection 
Obstetrics and gynecology  2011;118(4):831-839.
Objective
To describe the natural history of genital warts and vulvar intraepithelial neoplasia (VIN) in women with human immunodeficiency virus (HIV).
Methods
A cohort of 2,791 HIV infected and 953 uninfected women followed for up to 13 years had genital examinations at 6-month intervals, with biopsy for lesions suspicious for VIN.
Results
The prevalence of warts was 4.4% (5.3% for HIV seropositive women and 1.9% for seronegative women, P < 0.0001). The cumulative incidence of warts was 33% (95% C.I. 30, 36%) in HIV seropositive and 9% (95% C.I. 6, 12%) in seronegative women (P < 0.0001). In multivariable analysis, lower CD4 lymphocyte count, younger age, and current smoking were strongly associated with risk for incident warts. Among 501 HIV seropositive and 43 seronegative women, warts regressed in 410 (82%) seropositive and 41 (95%) seronegative women (P = 0.02), most in the first year after diagnosis. In multivariable analysis, regression was negatively associated with HIV status and lower CD4 count as well as older age. Incident VIN of any grade occurred more frequently among HIV seropositive than seronegative women: 0.42 (0.33 – 0.53) vs 0.07 (0.02 – 0.18)/100 person-years (P < 0.0001). VIN2+ was found in 58 women (55 with and 3 without HIV, P < 0.001). Two women with HIV developed stage IB squamous cell vulvar cancers.
Conclusion
While genital warts and VIN are more common among HIV seropositive than seronegative women, wart regression is common even in women with HIV, and cancers are infrequent.
doi:10.1097/AOG.0b013e31821a0f4d
PMCID: PMC3178036  PMID: 21934446
21.  Adipokines Linking Obesity with Colorectal Cancer Risk in Postmenopausal Women 
Cancer research  2012;72(12):3029-3037.
Mechanistic associations between obesity and colorectal cancer remain unclear. In this study, we investigated whether adipokines are risk factors for colorectal cancer and whether they may mediate its association with obesity. In a case–cohort study nested within the Women’s Health Initiative cohort of postmenopausal women, baseline plasma samples from 457 colorectal cancer cases and 841 subcohort subjects were assayed for seven adipokines—adiponectin, leptin, plasminogen activator inhibitor-1 (PAI-1), resistin, hepatocyte growth factor, interleukin-6 (IL-6), and TNF-α. Serum insulin and estradiol values measured previously were also available for data analysis. After adjusting for age, race, smoking, colonoscopy history, and estrogen level, a low level of antiinflammatory adiponectin and high levels of proinflammatory leptin, PAI-1, and IL-6 were associated with increased colorectal cancer risk, though only leptin remained significant after further adjustment for insulin [HRs comparing extreme quartiles (HRQ4–Q1), 1.84; 95% CI, 1.17–2.90]. Mediation analyses showed that leptin and insulin partially explained the association between waist circumference and colorectal cancer and attenuated it by 25% and 37%, respectively, with insulin being a significant mediator (P = 0.041). Our findings support the conclusion that adipokines involved in inflammation are associated with colorectal cancer risk, but that their effects may be mediated mostly by insulin, with leptin exerting an independent effect. Hyperinsulinemia and hyperleptinemia may therefore partially explain the adiposity association with colorectal cancer in postmenopausal women.
doi:10.1158/0008-5472.CAN-11-2771
PMCID: PMC3790260  PMID: 22511581
22.  Cervicovaginal HPV Infection Before and After Hysterectomy: Evidence of Different Tissue Tropism for Oncogenic and Non-Oncogenic HPV Types in a Cohort of HIV-positive and HIV-negative Women 
Human papillomavirus (HPV) is detected in nearly all cervical cancers and approximately half of vaginal cancers. However, vaginal cancer is an order of magnitude less common than cervical cancer, not only in the general population but also among women with HIV/AIDS. It is interesting therefore that recent studies found that HPV was common in both normal vaginal and cervical tissue, with higher prevalence of non-oncogenic HPV types in the vagina. In the current investigation, we prospectively examined HPV infection in 86 HIV-positive and 17 HIV-negative women who underwent hysterectomy during follow-up in a longitudinal cohort. Cervicovaginal lavage specimens were obtained semi-annually and tested for HPV DNA by PCR. To address possible selection biases associated with having a hysterectomy, subjects acted as their own comparison group – before versus after hysterectomy. The average HPV prevalence was higher in HIV-positive than HIV-negative women both before (59% versus 12%; P<0.001) and after hysterectomy (56% versus 6%; P<0.001). Multivariate random effects models (within-individual comparisons) demonstrated significantly lower HPV prevalence (odds ratio [OR]=0.71; 95% confidence interval [CI]=0.59-0.85) after hysterectomy. The association of HPV prevalence with hysterectomy was similar among HIV-positive and HIV-negative women. However, hysterectomy had greater effects on oncogenic (OR=0.48; 95%CI=0.35-0.66) than non-oncogenic HPV types (OR=0.89; 95%CI=0.71-1.11; Pinteraction=0.002). Overall, we observed greater reductions in oncogenic than non-oncogenic HPV prevalence following hysterectomy. If correct, these data could suggest that oncogenic HPV have greater tropism for cervical compared with vaginal epithelium, consistent with the lower incidence of vaginal than cervical cancer.
doi:10.1002/ijc.27363
PMCID: PMC3321069  PMID: 22120980
vaginal; HPV; hysterectomy; viral tropism; HIV
23.  Correlating knowledge of cervical cancer prevention and human papillomavirus with compliance after colposcopy referral 
Objective
To assess the impact of knowledge of cervical cancer biology and prevention as well as noncognitive measures on compliance with colposcopy referral in a high risk population.
Methods
Participants in a U.S. cohort of women with human immunodeficiency virus (HIV) and at risk comparison women completed behavior questionnaires and instruments measuring knowledge of cervical cancer prevention, depressive symptoms, trust in doctors, and perceived stress. Examinations including Pap tests also were conducted. Associations with compliance with resulting indicated colposcopy were assessed in multivariable models.
Results
Of 326 women with indicated colposcopy, 222 (68%) were compliant with colposcopy referral and 104 (32%) noncompliant. In multivariable analysis, better colposcopy compliance was associated with less education (O.R. for compliance 2.24, 95% C.I. 1.12–4.51 vs more than high school), prior abnormal Pap (O.R. per prior abnormal Pap 1.08 95% C.I. 1.01–1.15), study site (O.R. for site with best vs worst compliance 16.1, 95% C.I. 2.91–88.6), and higher stress (O.R. for Perceived Stress Scale-10 score >16 vs lower 3.25, 95% C.I. 1.45–7.26).
Conclusion
Noncognitive factors and how sites manage abnormal Pap testing affect colposcopy compliance. Educational interventions alone are unlikely to improve colposcopy compliance in similar high-risk populations.
doi:10.1097/LGT.0b013e318238e83d
PMCID: PMC3760241  PMID: 22227841
HPV; cervical cancer prevention; Pap test; health education; perceived stress; HIV in women
24.  A Comparison of the Polytomous Logistic Regression and Joint Cox Proportional Hazards Models for Evaluating Multiple Disease Subtypes in Prospective Cohort Studies 
Background
Polytomous logistic regression models are commonly used in case-control studies of cancer to directly compare the risks associated with an exposure variable across multiple cancer subtypes. However, the validity, accuracy and efficiency of this approach for prospective cohort studies have not been formally evaluated.
Methods
We investigated the performance of the polytomous logistic regression model and compared it to an alternative approach based on a joint Cox proportional hazards model using simulation studies. We then applied both methods to a prospective cohort study to assess whether the association of breast cancer with body size differs according to estrogen and progesterone receptor-defined subtypes.
Results
Our simulations showed that the polytomous logistic regression model but not the joint Cox regression model yielded biased results in comparing exposure and disease subtype associations when the baseline hazards for different disease subtypes are non-proportional. For this reason, an analysis of a real data set was based on the joint Cox proportional hazards model and showed that body size has a significantly greater association with estrogen and progesterone positive breast cancer than with other subtypes.
Conclusions
Because of the limitations of the polytomous logistic regression model for the comparison of exposure-disease associations across disease subtypes, the joint Cox proportional hazards model is recommended over the polytomous logistic regression model in prospective cohort studies.
Impact
The paper will promote the use of the joint Cox model in a prospective cohort study. Examples of SAS and S-plus programming codes are provided to facilitate use by non-statisticians.
doi:10.1158/1055-9965.EPI-12-1050
PMCID: PMC3565022  PMID: 23292084
time to event data; proportional hazards functions; robust variance; competing risk
25.  Testing the proportional hazards assumption in case-cohort analysis 
Background
Case-cohort studies have become common in epidemiological studies of rare disease, with Cox regression models the principal method used in their analysis. However, no appropriate procedures to assess the assumption of proportional hazards of case-cohort Cox models have been proposed.
Methods
We extended the correlation test based on Schoenfeld residuals, an approach used to evaluate the proportionality of hazards in standard Cox models. Specifically, pseudolikelihood functions were used to define “case-cohort Schoenfeld residuals”, and then the correlation of these residuals with each of three functions of event time (i.e., the event time itself, rank order, Kaplan-Meier estimates) was determined. The performances of the proposed tests were examined using simulation studies. We then applied these methods to data from a previously published case-cohort investigation of the insulin/IGF-axis and colorectal cancer.
Results
Simulation studies showed that each of the three correlation tests accurately detected non-proportionality. Application of the proposed tests to the example case-cohort investigation dataset showed that the Cox proportional hazards assumption was not satisfied for certain exposure variables in that study, an issue we addressed through use of available, alternative analytical approaches.
Conclusions
The proposed correlation tests provide a simple and accurate approach for testing the proportional hazards assumption of Cox models in case-cohort analysis. Evaluation of the proportional hazards assumption is essential since its violation raises questions regarding the validity of Cox model results which, if unrecognized, could result in the publication of erroneous scientific findings.
doi:10.1186/1471-2288-13-88
PMCID: PMC3710085  PMID: 23834739
Proportional hazards; Schoenfeld residuals; Case-cohort studies; Cox models

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