Introduction

Studies on the association of a polymorphism in codon 72 of the p53 tumour suppressor gene (rs1042522) with cervical neoplasia have inconsistent results. While several methods for genotyping p53 exist, they vary in accuracy and are often discrepant.

Methods

We used latent class models (LCM) to examine the accuracy of six methods for p53 determination, all conducted by the same laboratory. We also examined the association of p53 with cytological cervical abnormalities, recognising potential test inaccuracy.

Results

Pairwise disagreement between laboratory methods occurred approximately 10% of the time. Given the estimated true p53 status of each woman, we found that each laboratory method is most likely to classify a woman to her correct status. Arg/Arg women had the highest risk of squamous intraepithelial lesions (SIL). Test accuracy was independent of cytology. There was no strong evidence for correlations of test errors.

Discussion

Empirical analyses ignore possible laboratory errors, and so are inherently biased, but test accuracy estimated by the LCM approach is unbiased when model assumptions are met. LCM analysis avoids ambiguities arising from empirical test discrepancies, obviating the need to regard any of the methods as a “gold” standard measurement. The methods we presented here to analyse the p53 data can be applied in many other situations where multiple tests exist, but where none of them is a gold standard.

Life expectancy has risen sharply in the last 50 years. We applied the classic Michaelis–Menten enzyme kinetics to demonstrate a novel mathematical relationship of income to childhood (aged 0–5 years) and adult (aged 15–60 years) survival. We treat income as a substrate that is catalyzed to increase survival (from technologies that income buys) for 180 countries from 1970 and 2007. Michaelis–Menten kinetics permit estimates of maximal survival and, uniquely, the critical income needed to achieve half of the period-specific maximum. Maximum child and adult survival rose by about 1% per year. Critical incomes fell by half for children, but doubled for men. HIV infection and smoking account for some, but not all, of the rising critical incomes for adult survival. Altering the future cost curve for adult survival will require more widespread use of current interventions, most notably tobacco control, but also research to identify practicable low-cost drugs, diagnostics, and strategies.

DOI: http://dx.doi.org/10.7554/eLife.00051.001

eLife digest

In 1975 Samuel Preston published a classic paper that showed life expectancy was related to national income. When plotted as a graph, with national income on the horizontal axis and life expectancy on the vertical axis, the Preston curve shows that an increase in national income leads to an increase in life expectancy, with the increases in life expectancy becoming proportionally smaller as income increases. Moreover, Preston showed that innovations in healthcare (such as vaccinations, public health education, and sanitation systems) were increasing the maximum life expectancy that can be achieved for any given national income (defined as GDP per capita): this can be seen by comparing the Preston curves from 1960 and 2000 shown in Figure 1A. Indeed, global life expectancy increased by about 25 years over the course of the 20th century, which suggests that the level of daily income needed to achieve a certain life expectancy should be falling over time.

To explore this in greater detail, Hum et al. have constructed a mathematical model to investigate the relationship between health and income across different age groups and income levels. They found that most of the gains in life expectancy for low- and middle-income countries have been achieved by reducing child mortality, with gains in life expectancy for adults being restricted mostly to high-income countries. The model, which is based on the mathematical equations used to describe the kinetics of enzymatic reactions, makes it possible to estimate the improvements of health that can be made over time, and also the level of income that is needed to achieve these improvements.

In particular, Hum et al. have established a new parameter, the critical income, which is the level of income needed to achieve half of the maximal health found in high-income countries for the year in question. Based on available data from over 150 countries, they found that critical incomes fell by half for children between 1970 and 2007, but doubled for adult males during the same period. The rise in critical income for adults was due partly to the HIV epidemic and increases in smoking in low- and middle-income countries, reflecting the growing problems presented by noncommunicable diseases. Hum et al. conclude that increasing the survival among adults will require increased use of proven cost-effective interventions, most notably tobacco control, plus new research to identify low-cost drugs, diagnostics, and other public health strategies.

DOI: http://dx.doi.org/10.7554/eLife.00051.002

A systematic review and meta-analysis of randomized trials conducted by B. Joseph Elmunzer and colleagues reports that that flexible sigmoidoscopy-based screening reduces the incidence of colorectal cancer in average-risk patients, as compared to usual care or no screening.

Background

Randomized controlled trials (RCTs) have yielded varying estimates of the benefit of flexible sigmoidoscopy (FS) screening for colorectal cancer (CRC). Our objective was to more precisely estimate the effect of FS-based screening on the incidence and mortality of CRC by performing a meta-analysis of published RCTs.

Methods and Findings

Medline and Embase databases were searched for eligible articles published between 1966 and 28 May 2012. After screening 3,319 citations and 29 potentially relevant articles, two reviewers identified five RCTs evaluating the effect of FS screening on the incidence and mortality of CRC. The reviewers independently extracted relevant data; discrepancies were resolved by consensus. The quality of included studies was assessed using criteria set out by the Evidence-Based Gastroenterology Steering Group. Random effects meta-analysis was performed.

The five RCTs meeting eligibility criteria were determined to be of high methodologic quality and enrolled 416,159 total subjects. Four European studies compared FS to no screening and one study from the United States compared FS to usual care. By intention to treat analysis, FS-based screening was associated with an 18% relative risk reduction in the incidence of CRC (0.82, 95% CI 0.73–0.91, p<0.001, number needed to screen [NNS] to prevent one case of CRC = 361), a 33% reduction in the incidence of left-sided CRC (RR 0.67, 95% CI 0.59–0.76, p<0.001, NNS = 332), and a 28% reduction in the mortality of CRC (relative risk [RR] 0.72, 95% CI 0.65–0.80, p<0.001, NNS = 850). The efficacy estimate, the amount of benefit for those who actually adhered to the recommended treatment, suggested that FS screening reduced CRC incidence by 32% (p<0.001), and CRC-related mortality by 50% (p<0.001).

Limitations of this meta-analysis include heterogeneity in the design of the included trials, absence of studies from Africa, Asia, or South America, and lack of studies comparing FS with colonoscopy or stool-based testing.

Conclusions

This meta-analysis of randomized controlled trials demonstrates that FS-based screening significantly reduces the incidence and mortality of colorectal cancer in average-risk patients.

Please see later in the article for the Editors' Summary

Editor's Summary

Background

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Regular CRC screening has been shown to reduce the risk of dying from CRC by 16%, and CRC screening can identify early stage cancers in otherwise healthy people, which allows for early treatment and management of the disease. Screening for colorectal cancer is frequently performed using a flexible sigmoidoscopy (FS), which is a thin, flexible tube with a tiny camera and light on the end, allowing a doctor to look at the inside wall of the bowel and remove any small growths or polyps. Although screening may detect early cancers, the life-saving and health benefits of screening are uncertain because the polyp may not necessarily progress. This could lead to anxiety and unnecessary interventions and treatments amongst those screened. Randomized controlled trials (RCTs) are needed to determine all of the risks involved in cancer screenings, however the guidelines that recommend FS-based screening do not rely upon RCT data. Recently, the results of four large-scale RCTs evaluating FS screening for CRC have been published. The conflicting results with respect to the incidence and mortality of CRC in these studies have called into question the effectiveness of endoscopic screening.

Why Was This Study Done?

The results of RCTs measuring the risks and outcomes of CRC screening have shown varying estimates of the benefits of using FS screening. If better estimates of the risks and benefits of FS screening are developed, then the current CRC screening guidelines may be updated to reflect this new information. In this study, the authors show the results of a meta-analysis of published RCTs, which more precisely estimates the effects of FS-based screening on the incidence and mortality of colorectal cancer.

What Did the Researchers Do and Find?

The researchers used the Medline and Embase databases to find relevant studies from 1966 to May 28, 2012. After screening 3,319 citations and 29 potentially relevant articles, five RCTs of high methodologic quality and 416,159 total subjects evaluating the effect of FS screening on the incidence and mortality of CRC were identified. The data were extracted and random effects meta-analysis was performed. The meta-analysis revealed that FS-based screening was associated with an 18% relative risk reduction in the incidence of CRC (0.82, 95% CI 0.73–0.91, p<0.001, number needed to screen (NNS) to prevent one case of CRC = 361), a 33% reduction in the incidence of left-sided CRC (RR 0.67, 95% CI 0.59–0.76, p<0.001, NNS = 332), and a 28% reduction in the mortality of CRC (RR 0.72, 95% CI 0.65–0.80, p<0.001, NNS = 850). The amount of benefit for those who adhered to the recommended treatment suggested that FS screening reduced CRC incidence by 32% (p<0.001), and CRC-related mortality by 50% (p<0.001).

What Do These Findings Mean?

This meta-analysis of RCTs evaluating the effect of FS on CRC incidence and mortality demonstrates that a FS-based strategy for screening is very effective in reducing the incidence and mortality of CRC in patients. The current recommendations for endoscopic screening are based on observational studies, which may not accurately reflect the effect of FS-based screening on the incidence and mortality of CRC. Here, the authors performed a systematic review and meta-analysis of five recent RCTs to better estimate the true effect of FS-based screening on the incidence and mortality of CRC. Thus, the results of this meta-analysis may affect health policy, and directly impact patients and clinicians.

Additional Information

Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001352.

Cancer research UK provides comprehensive information about screening for colorectal cancers as does the UK National Screening Committee

PubMed Health has general information about colon cancer

The National Cancer Institute also has comprehensive resources on colorectal cancer and treatment

The Mayo Clinic provides an overview of all aspects of colon cancer

We estimated human papillomavirus (HPV) transmission rates among persons with documented sexual exposure to an infected partner. Recently formed couples enrolled in the HITCH Study (HPV Infection and Transmission among Couples through Heterosexual activity) in Montreal, Canada, and provided genital specimens for DNA testing of 36 HPV genotypes. At enrollment, 179 couples were discordant for ≥1 HPV types; transmission was observed at follow-up in 73 partnerships. There was little difference between the male-to-female (3.5 per 100 person-months, 95% confidence interval [CI], 2.7–4.5) and female-to-male (4.0 per 100 person-months, 95% CI, 3.0–5.5) transmission rates. Rates did not vary with the lifetime number of partners reported by the initially uninfected partner, providing no evidence of reduced susceptibility for those with extensive sexual histories. Transmission was also relatively homogeneous across HPV genotypes and alpha species and oncogenic risk categories. The findings contribute to a small but growing evidence base regarding the natural history of HPV transmission.

Background

Human papillomavirus type 97 (HPV97) DNA was detected in nearly 5% of anal samples collected from HIV-seropositive men living in Montreal, Canada. The rate of detection of HPV97 in the genital tract of Canadian women is unknown. Whether HPV97 is a local epidemic in HIV-seropositive men living in Montreal is also unknown. The prevalence of human papillomavirus type 97 (HPV97) was assessed in cervicovaginal cells from women living in Canada and in anal samples from HIV-seropositive men living in Toronto.

Findings

Cervicovaginal lavages collected from 904 women (678 HIV-seropositive, 226 HIV-seronegative) women living in Canada and anal cells collected from 123 HIV-seropositive men living in Toronto were tested for the presence of HPV97 with PCR. HPV97-positive samples were further tested by PCR-sequencing for molecular variant analysis to assess if all HPV97-positive men were infected with the same strain. All cervicovaginal samples were negative for HPV97. HPV97 was detected in anal samples from 6 HIV-seropositive men (4.9%, 95% confidence interval 2.0-10.5%), of whom five had high-grade and one had low-grade anal intraepithelial neoplasia, in addition to 2 to 8 HPV genital genotypes per sample. Four HPV97 variants were defined by four variation sites in the viral control region.

Conclusion

These findings indicate that HPV97 infects in the anal canal of HIV-seropositive men but is not detected in the genital tract of women.

The triage of women with high-risk (HR) human papillomavirus (HPV)-positive smears for atypical squamous cells of undetermined significance (ASC-US) to colposcopy is now an integrated option in clinical guidelines. The performance of cobas 4800 HPV and that of Hybrid Capture 2 (HC2) for HR HPV DNA detection in cervical samples in PreservCyt were compared in 396 women referred to colposcopy for ASC-US. Of these, 316 did not have cervical intraepithelial neoplasia (CIN), 47 had CIN1, 29 had CIN2 or CIN3 (CIN2+), and 4 had CIN of unknown grade. HR HPV was detected in 129 (32.6%) and 149 (37.6%) samples with HC2 and cobas 4800 HPV, respectively (P = 0.15). The clinical sensitivities and specificities for detecting CIN2+ were 89.7% (95% confidence interval [CI], 72.8 to 97.2%) and 66.7% (95% CI, 61.7 to 71.3%) with cobas 4800 HPV and 93.1% (95% CI, 77.0 to 99.2%) and 72.2% (95% CI 67.4 to 76.5%) with HC2. The performance of cobas 4800 HPV was similar to that of HC2 for identifying women with ASC-US who would benefit the most from colposcopy.

Although oncogenic HPV infections have been established as the necessary cause of cervical cancer, most HPV infections are transient and rarely progress to cervical lesions. Current research is focused on identifying factors associated with viral persistence and clearance, such as nutritional status. We evaluated the association between serum antioxidant nutrients (retinol, 10 carotenoids and 3 tocopherols) and type-specific HPV persistence over 4 visits among 405 women participating in the Ludwig-McGill cohort study. We measured circulating carotenoids and tocopherol at 4 different clinical visits for each woman. We report the results from different analytic approaches (a case–control approach at both the woman and viral level, and a prospective approach based on persistent events) that examined the association between these micronutrients and type-specific oncogenic and nononcogenic HPV persistence. In the case–control analysis at the viral level, midcirculating levels of α-tocopherol were inversely associated with nononcogenic HPV persistent infection (adjusted odds ratio (AOR) = 0.28, 95% CI 0.14–0.57), while high levels were marginally associated (AOR = 0.59, 95% CI 0.28–1.19). Similarly, utilizing generalized estimating equation models, circulating levels of α- and δ-tocopherol in the middle or upper tertiles were inversely associated with type-specific nononcogenic HPV persistence (AOR = 0.44, 95% CI 0.19–0.97 and AOR = 0.46, 95% CI 0.19–1.11, respectively). Our study among Brazilian women suggests that serum levels of tocopherols may be protective against nononcogenic HPV persistence. However, we did not find a strong protective effect (as hypothesized) of other serum antioxidant nutrients and type-specific oncogenic HPV persistence measured over 4 clinical visits.

Few biomarkers are available to predict prostate cancer risk. Single nucleotide polymorphisms (SNPs) tend to have weak individual effects but, in combination, they have stronger predictive value. Adipokine pathways have been implicated in the pathogenesis. We used a candidate pathway approach to investigate 29 functional SNPs in key genes from relevant adipokine pathways in a sample of 1006 men eligible for prostate biopsy. We used stepwise multivariate logistic regression and bootstrapping to develop a multilocus genetic risk score by weighting each risk SNP empirically based on its association with disease. Seven common functional polymorphisms were associated with overall and high-grade prostate cancer (Gleason≥7), whereas three variants were associated with high metastatic-risk prostate cancer (PSA≥20 ng/mL and/or Gleason≥8). The addition of genetic variants to age and PSA improved the predictive accuracy for overall and high-grade prostate cancer, using either the area under the receiver-operating characteristics curves (P<0.02), the net reclassification improvement (P<0.001) and integrated discrimination improvement (P<0.001) measures. These results suggest that functional polymorphisms in adipokine pathways may act individually and cumulatively to affect risk and severity of prostate cancer, supporting the influence of adipokine pathways in the pathogenesis of prostate cancer. Use of such adipokine multilocus genetic risk score can enhance the predictive value of PSA and age in estimating absolute risk, which supports further evaluation of its clinical significance.

A generic human papillomavirus (HPV) probe assay was compared to the Linear Array to detect HPV DNA in 1,013 clinical specimens. The sensitivity, specificity, and negative predictive value of the assay were 99.5% (95% confidence interval [CI], 98.4% to 99.9%), 58.6% (95% CI, 53.9% to 63.1%), and 98.9% (95% CI, 96.5% to 99.8%), respectively. This assay conveniently identifies HPV-positive specimens.

A reanalysis of published and unpublished data from epidemiological studies examines the association between height, body mass index, and the risk of developing ovarian cancer.

Background

Only about half the studies that have collected information on the relevance of women's height and body mass index to their risk of developing ovarian cancer have published their results, and findings are inconsistent. Here, we bring together the worldwide evidence, published and unpublished, and describe these relationships.

Methods and Findings

Individual data on 25,157 women with ovarian cancer and 81,311 women without ovarian cancer from 47 epidemiological studies were collected, checked, and analysed centrally. Adjusted relative risks of ovarian cancer were calculated, by height and by body mass index.

Ovarian cancer risk increased significantly with height and with body mass index, except in studies using hospital controls. For other study designs, the relative risk of ovarian cancer per 5 cm increase in height was 1.07 (95% confidence interval [CI], 1.05–1.09; p<0.001); this relationship did not vary significantly by women's age, year of birth, education, age at menarche, parity, menopausal status, smoking, alcohol consumption, having had a hysterectomy, having first degree relatives with ovarian or breast cancer, use of oral contraceptives, or use of menopausal hormone therapy. For body mass index, there was significant heterogeneity (p<0.001) in the findings between ever-users and never-users of menopausal hormone therapy, but not by the 11 other factors listed above. The relative risk for ovarian cancer per 5 kg/m2 increase in body mass index was 1.10 (95% CI, 1.07–1.13; p<0.001) in never-users and 0.95 (95% CI, 0.92–0.99; p = 0.02) in ever-users of hormone therapy.

Conclusions

Ovarian cancer is associated with height and, among never-users of hormone therapy, with body mass index. In high-income countries, both height and body mass index have been increasing in birth cohorts now developing the disease. If all other relevant factors had remained constant, then these increases in height and weight would be associated with a 3% increase in ovarian cancer incidence per decade.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Cancer of the ovaries, usually referred to as ovarian cancer, is the fifth leading cause of cancer death in women, and, unfortunately, symptoms (such as abdominal pain and swelling) usually occur late in the disease process; fewer than one-third of ovarian cancers are detected before they have spread outside of the ovaries. There is no definitive evidence that screening reduces mortality from ovarian cancer, and given the poor prognosis of advanced ovarian cancer, there has been much research over recent years to increase understanding of this serious condition. There are recognized risk factors that increase the chance of developing ovarian cancer, such as increasing age, having fewer children, not having used oral contraceptives, and use of menopausal hormone therapy. Age and oral contraceptive use have by far the biggest impact on ovarian cancer risk.

Why Was This Study Done?

To date, there is no definitive information about the relevance of women's height, weight, and body mass index to their subsequent risk of developing ovarian cancer. There have been roughly 50 epidemiological studies of ovarian cancer, but only about half of these studies have published results on the association between body size and ovarian cancer risk, and so far, these findings have been inconsistent. Therefore, the researchers—an international collaboration of researchers studying ovarian cancer—re-analyzed the available epidemiological evidence to investigate the relationship between ovarian cancer risk and adult height, weight, and body mass index, and to examine the consistency of the findings across study designs.

What Did the Researchers Do and Find?

After an extensive literature search, the researchers identified 47 eligible studies that collected individual data on women's reproductive history, use of hormonal therapies, height, weight, and/or body mass index, and in which the principal investigators of each study accepted the invitation from the researchers to be involved in the re-analysis. The researchers combined data from the different studies. To ensure that women in one study were only directly compared with controls (similar women without ovarian cancer) in the same study, all analyses were routinely stratified by study, center within study, age, parity, use of oral contraceptives, use of hormonal therapy for menopause, and menopausal status or hysterectomy.

The 47 studies were conducted in 14 countries and comprised a total of 25,157 women with ovarian cancer (mostly from Europe and North America) and 81,311 women without ovarian cancer. The researchers found a significant increase in relative risk (1.07) of ovarian cancer per 5 cm increase in height. Furthermore, this risk did not vary depending on other studied factors—age, year of birth, education, age at menarche, parity, menopausal status, smoking, alcohol consumption, having had a hysterectomy, having first degree relatives with ovarian or breast cancer, use of oral contraceptives, or use of menopausal hormone therapy. However, the researchers found that for body mass index, the risks depended on whether women had ever taken menopausal hormone therapy: the relative risk for ovarian cancer per 5 kg/m2 increase in body mass index was 1.10 in women who had never taken menopausal hormone therapy but was only 0.95 in women who had previously taken menopausal hormone therapy.

What Do These Findings Mean?

These findings suggest that increasing height can be considered as a risk factor for ovarian cancer and that in women who have never taken menopausal hormone therapy, increased body mass index can be considered an additional risk factor. These findings have public health implications, especially in high-income countries, because the average height of women has increased by about 1 cm per decade and average body mass index has increased by about 1 kg/m2 per decade. The findings suggest an associated increase in ovarian cancer incidence of 3% per decade if all other factors relevant for ovarian cancer remain constant.

Additional Information

Please access these web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001200.

The following organizations give more information on ovarian cancer which may be of use to patients: MedicineNet, the US National Cancer Institute, Ovarian Cancer National Alliance, Macmillan Cancer Support

A case-control study conducted in South Africa provides new estimates of the risk of specific cancers of the female reproductive system associated with use of injectable and oral contraceptives.

Background

Oral contraceptives are known to influence the risk of cancers of the female reproductive system. Evidence regarding the relationship between injectable contraceptives and these cancers is limited, especially in black South Africans, among whom injectable contraceptives are used more commonly than oral contraceptives.

Methods and Findings

We analysed data from a South African hospital-based case–control study of black females aged 18–79 y, comparing self-reported contraceptive use in patients with breast (n = 1,664), cervical (n = 2,182), ovarian (n = 182), and endometrial (n = 182) cancer, with self-reported contraceptive use in 1,492 control patients diagnosed with cancers with no known relationship to hormonal contraceptive use. We adjusted for potential confounding factors, including age, calendar year of diagnosis, education, smoking, alcohol, parity/age at first birth, and number of sexual partners. Among controls, 26% had used injectable and 20% had used oral contraceptives. For current and more recent users versus never users of oral or injectable contraceptives, the odds ratios (ORs) for breast cancer were significantly increased in users of oral and/or injectable contraceptives (OR 1.66, 95% CI 1.28–2.16, p<0.001) and separately among those exclusively using oral (1.57, 1.03–2.40, p = 0.04) and exclusively using injectable (OR 1.83, 1.31–2.55, p<0.001) contraceptives; corresponding ORs for cervical cancer were 1.38 (1.08–1.77, p = 0.01), 1.01 (0.66–1.56, p = 0.96), and 1.58 (1.16–2.15, p = 0.004). There was no significant increase in breast or cervical cancer risk among women ceasing hormonal contraceptive use ≥10 y previously (p = 0.3 and p = 0.9, respectively). For durations of use ≥5 y versus never use, the ORs of ovarian cancer were 0.60 (0.36–0.99, p = 0.04) for oral and/or injectable contraceptive use and 0.07 (0.01–0.49, p = 0.008) for injectable use exclusively; corresponding ORs for endometrial cancer were 0.44 (0.22–0.86, p = 0.02) and 0.36 (0.11–1.26, p = 0.1).

Conclusions

In this study, use of oral and of injectable hormonal contraceptives was associated with a transiently increased risk of breast and cervical cancer and, for long durations of use, with a reduced risk of ovarian and endometrial cancer. The observed effects of injectable and of oral contraceptives on cancer risk in this study did not appear to differ substantially.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Hormonal contraceptives are among the most commonly used medications. Globally, more than 210 million women currently use either hormonal contraceptive pills or injectable contraceptives. Contraceptive pills usually contain manmade versions of the female sex hormones estrogen and progesterone (the combined oral contraceptive, or “pill”); most injectable hormonal contraceptives contain only manmade progesterone preparations. Hormonal contraceptives, which prevent pregnancy by disrupting the cyclical changes in estrogen and progesterone levels that prepare the body for pregnancy, have revolutionized birth control since they first became available in the early 1960s. However, it is now known that taking the pill also influences women's risk of developing cancers of the female reproductive system. Current and recent users have an increased risk of developing breast and cervical cancer (the cervix is the structure that connects the womb to the vagina) compared to never users, although this increased risk quickly disappears when women stop taking the pill. By contrast, women who have used the pill have a reduced risk of developing ovarian cancer and cancer of the womb (endometrial cancer) compared to never users that increases with the duration of pill use and persists for many years after use ceases. These effects on reproductive system cancers are thought to occur because these cancers depend on naturally occurring sex hormones for their development and growth.

Why Was This Study Done?

Although the evidence that the pill influences the risk of developing cancers of the female reproductive system is extensive, much less is known about how injectable hormonal contraceptives affect cancer risk. In this hospital-based case–control study (a study that compares the characteristics of people with and without a specific condition), the researchers investigate the relationship between the use of oral and injectable hormonal contraceptives and cancers of the breast, cervix, ovary, and endometrium among black South African women. Injectable contraceptives have been used for longer in South Africa than elsewhere and are used more commonly than oral contraceptives among black South African women.

What Did the Researchers Do and Find?

As part of the Johannesburg Cancer Case Control Study, which recruits black patients attending Johannesburg public referral hospitals for cancer treatment, the researchers compared hormonal contraceptive use in women with breast, cervical, ovarian, or endometrial cancer with contraceptive use in women diagnosed with other cancers such as lung, colon, and rectal cancers, which are not known to be influenced by hormonal contraceptives. Among the controls, a quarter had used injectable contraceptives and a fifth had used oral contraceptives. After adjusting for other factors that might influence cancer risk such as age, smoking, and number of sexual partners, the odds ratio (OR) of breast cancer among current and recent users of oral and/or injectable contraceptives compared to never users was 1.66. That is, the risk of developing breast cancer among current and recent users of hormonal contraceptives was 1.66 times that among never users. For women using oral contraceptives exclusively or injectable contraceptives exclusively, the ORs of breast cancer were 1.57 and 1.83, respectively. There were also increases in cervical cancer risk among current and recent users of hormonal contraceptives compared to never users, but no significant increase in breast or cervical cancer risk among women who had ceased hormonal contraceptive use more than ten years previously. Finally, the use of hormonal contraceptives for more than five years reduced the risk of both ovarian and endometrial cancer.

What Do These Findings Mean?

These findings indicate that, among black women in South Africa, the use of oral or injectable hormonal contraceptives is associated with a transiently increased risk of breast and cervical cancer, and that extended use of these contraceptives is associated with a reduced risk of ovarian and endometrial cancer. Moreover, they suggest that the effects of oral versus injectable contraceptives on cancer risk do not differ substantially, although for endometrial and ovarian cancer the small number of cases exposed to injectable contraceptives limits the accuracy of the risk estimates. Other limitations of this study include the possibility that the findings may be affected by uncontrolled confounding. That is, women who used hormonal contraceptives may have shared other unidentified characteristics that affected their cancer risk. Nevertheless, these findings provide new information about the effects of oral and injectable hormonal contraceptives on cancer risk that should help women make informed decisions about their choice of contraceptive method.

Additional Information

Please access these web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001182.

The US National Cancer Institute provides information on breast cancer (including personal stories from breast cancer survivors), cervical cancer, ovarian cancer, and endometrial cancer for patients and health professionals, and a fact sheet on oral contraceptives and cancer risk (in English and Spanish)

Cancer Research UK also provides information on breast cancer, cervical cancer, ovarian cancer, and endometrial cancer and information about the birth control pill and cancer risk

Eyes on the Prize, an online support group for women who have had cancers of the female reproductive system, has personal stories; further personal stories about breast, cervical, and ovarian cancer are provided by the charity Healthtalkonline

Objectives

To describe the attitudes about and experiences with cervical cancer, Pap smear screenings and the HPV vaccine among a sample of Inuit women from Nunavik, Quebec, Canada. We also evaluated demographic and social predictors of maternal interest in HPV vaccination.

Study design

A mixed method design was used with a cross-sectional survey and focus group interviews.

Methods

Women were recruited through convenience sampling at 2 recruitment sites in Nunavik from March 2008 to June 2009. Differences in women's responses by age, education, and marital status were assessed. Unconditional logistic regression was used to determine predictors of women's interest in HPV vaccination for their children.

Results

Questionnaires were completed by 175 women aged 18–63, and of these women a total of 6 women aged 31–55 participated in 2 focus groups. Almost half the survey participants had heard of cervical cancer. Women often reported feelings of embarrassment and pain during the Pap smear and older women were more likely to feel embarrassed than younger women. Only 27% of women had heard of the HPV vaccine, and 72% of these women were interested in vaccinating their child for HPV. No statistically significant predictors of maternal interest in HPV vaccination were found.

Conclusions

Our findings indicate that health service planners and providers in Nunavik should be aware of potential barriers to Pap smear attendance, especially in the older age groups. Given the low awareness of cervical cancer, the Pap smear and the HPV vaccine, education on cervical cancer and prevention strategies may be beneficial.1

Background

Although oncogenic human papillomavirus (HPV) infections have been established as the necessary cause of cervical cancer, most HPV infections are transient and rarely progress to squamous cervical lesions. The activity of HPV is tightly associated with epithelial cell differentiation; therefore regulators of differentiation, such as retinoic acid, have been considered targets for the prevention of HPV-associated squamous intraepithelial lesion (SIL) development.

Purpose

The purpose of this study was to determine the association between circulating retinoic acid (RA) and early events in cervical carcinogenesis, specifically type-specific HPV clearance and SIL detection.

Methods

Archived blood samples from 643 women participating in the Ludwig-McGill Cohort in São Paulo, Brazil were analyzed by high-pressure liquid chromatography for three RA isomers (all-trans, 13-cis, and 9-cis RA). A type-specific HPV clearance event was defined as two consecutive visits negative for that HPV type during follow-up for the 364 HPV positive women. Among the 643 women in this analysis, 78 were diagnosed with incident SIL.

Results

The probability of clearing an oncogenic HPV infection was not significantly different across RA isomer quartiles. There was a suggestion that increasing all-trans RA increased rate of non-oncogenic HPV clearance (p-trend=0.05). There was no association observed between serum RA levels and incident SIL.

Conclusions

Our results suggest that elevated circulating RA isomer levels do not increase rates of HPV clearance or reduce risk of incident SIL. The role of RA in the inhibition of HPV induced carcinogenesis, as demonstrated in vitro, lacks confirmatory evidence within epidemiologic studies among women.

Objective. To investigate the accuracy of dies obtained from single-step and 2-step double-mix impressions. Material and Methods. Impressions (n = 10) of a stainless steel die simulating a complete crown preparation were performed using a polyether (Impregum Soft Heavy and Light body) and a vinyl polysiloxane (Perfectim Blue Velvet and Flexi-Velvet) in two consistencies, in one or two (without relief) steps. Accuracy of the stone dies was accessed at a measuring microscope, using a metallic crown with perfect fit to the reference crown preparation. Data were submitted to 2-way ANOVA and Tukey test (α = 0.05). Results. The single-step technique resulted in slightly larger dies, while the 2-step technique without relief produced significantly smaller dies, when compared to the original stainless steel die. Stone dies obtained from 2-step polyether impressions were significantly smaller when compared to dies obtained from 2-step vinyl polysiloxane impressions (Impregum 2-step: −290.94 ± 71.64 μm; Perfectim 2-step: −201.86 ± 28.58 μm). No significant differences were observed in dies obtained from either polyether or vinyl polysiloxane with the single-step technique (Impregum single-step: 63.52 ± 16.60 μm; Perfectim single-step: 79.40 ± 14.11 μm). Conclusion. Higher discrepancies were detected for the 2-step impression technique without relief for the investigated materials.

Up to 20% of women having a cytology smear showing atypical squamous cells of undetermined significance (ASC-US) and infected with high-risk human papillomavirus (HR HPV) have high-grade cervical intraepithelial neoplasia (CIN 2/3). Results obtained with the Amplicor HPV and Hybrid Capture 2 (HC-2) assays for HR HPV DNA detection in women referred to colposcopy for an ASC-US smear were compared. Cervical samples in PreservCyt were tested for the presence of 13 HR HPV types with HC-2, with Amplicor at three cutoffs for positivity (0.2, 1.0, and 1.5 optical density units), and for 36 genotypes with the Linear Array (LA). Of 396 eligible women, 316 did not have CIN, 47 had CIN 1, 29 had CIN 2/3, and 4 had CIN of unknown grade. HR HPV was detected in 129 (32.6%) and 164 (41.4%) samples with HC-2 and Amplicor HPV (cutoff, 0.2), respectively (P = 0.01). Overall, 112 specimens were positive and 215 were negative with the HC-2 and Amplicor HPV assays (agreement of 82.6%; 95% confidence interval [CI], 78.5 to 86.0). The clinical sensitivity and specificity of Amplicor HPV at cutoffs of 0.2, 1.0 and 1.5 and of HC-2 for detection of CIN 2/3 were 89.7% (95% CI, 72.8 to 97.2) and 62.5% (95% CI, 57.5 to 52.4), 89.7% (95% CI, 72.8 to 97.2) and 64.5% (95% CI, 59.4 to 69.2), 89.7% (95% CI, 72.8 to 97.2) and 64.7% (95% CI, 59.7 to 69.5), and 93.1% (95% CI, 77.0 to 99.2) and 72.2% (95% CI, 67.4 to 76.5), respectively. Both HR HPV detection tests identified women with ASC-US who would benefit the most from colposcopy. Women with persistent HR HPV infection need further investigation despite a first normal colposcopy.

Background

Despite strong laboratory evidence that non-steroidal anti-inflammatory drugs (NSAIDs) could prevent prostate cancer, epidemiological studies have so far reported conflicting results. Most studies were limited by lack of information on dosage and duration of use of the different classes of NSAIDs.

Methods

We conducted a nested case-control study using data from Saskatchewan Prescription Drug Plan (SPDP) and Cancer Registry to examine the effects of dose and duration of use of five classes of NSAIDs on prostate cancer risk. Cases (N = 9,007) were men aged ≥40 years diagnosed with prostatic carcinoma between 1985 and 2000, and were matched to four controls on age and duration of SPDP membership. Detailed histories of exposure to prescription NSAIDs and other drugs were obtained from the SPDP.

Results

Any use of propionates (e.g., ibuprofen, naproxen) was associated with a modest reduction in prostate cancer risk (Odds ratio = 0.90; 95%CI 0.84-0.95), whereas use of other NSAIDs was not. In particular, we did not observe the hypothesized inverse association with aspirin use (1.01; 0.95–1.07). There was no clear evidence of dose-response or duration-response relationships for any of the examined NSAID classes.

Conclusions

Our findings suggest modest benefits of at least some NSAIDs in reducing prostate cancer risk.

Epidemiologists are well aware of the negative consequences of measurement error in exposure and outcome variables to their ability to detect putative causal associations. However, empirical proof that remedying the misclassification problem improves estimates of epidemiologic effect is seldom examined in detail. Of all areas in cancer epidemiology, perhaps the best example of the consequences of misclassification and of the steps taken to circumvent them was the pursuit, beginning in the mid-1980s, of the human papillomavirus (HPV) infection–cervical cancer association. The stakes were high: Had the wrong conclusions been reached epidemiologists would have been led astray in the search for competing hypotheses for the sexually transmissible agent causing cervical cancer or in ascribing to HPV infection a mere ancillary role among many lifestyle, hormonal, and environmental factors. The article by Castle et al. in this issue of the Journal (Am J Epidemiol. 2010;171(2):155–163) provides a detailed account of the joint influences of improved HPV and cervical precancer measurements in gradually unveiling the strong magnitude of the underlying association between viral exposure and cervical lesion risk. In this commentary, the authors extend the findings of Castle et al. by providing additional empirical evidence in support of their arguments.

An economic analysis of different screening methods for detection of colorectal cancers suggests that in US or Canadian settings, screening with fecal immunochemical testing results in lower health-care costs as compared with other screening approaches.

Background

Colorectal cancer (CRC) fulfills the World Health Organization criteria for mass screening, but screening uptake is low in most countries. CRC screening is resource intensive, and it is unclear if an optimal strategy exists. The objective of this study was to perform an economic evaluation of CRC screening in average risk North American individuals considering all relevant screening modalities and current CRC treatment costs.

Methods and Findings

An incremental cost-utility analysis using a Markov model was performed comparing guaiac-based fecal occult blood test (FOBT) or fecal immunochemical test (FIT) annually, fecal DNA every 3 years, flexible sigmoidoscopy or computed tomographic colonography every 5 years, and colonoscopy every 10 years. All strategies were also compared to a no screening natural history arm. Given that different FIT assays and collection methods have been previously tested, three distinct FIT testing strategies were considered, on the basis of studies that have reported “low,” “mid,” and “high” test performance characteristics for detecting adenomas and CRC. Adenoma and CRC prevalence rates were based on a recent systematic review whereas screening adherence, test performance, and CRC treatment costs were based on publicly available data. The outcome measures included lifetime costs, number of cancers, cancer-related deaths, quality-adjusted life-years gained, and incremental cost-utility ratios. Sensitivity and scenario analyses were performed. Annual FIT, assuming mid-range testing characteristics, was more effective and less costly compared to all strategies (including no screening) except FIT-high. Among the lifetimes of 100,000 average-risk patients, the number of cancers could be reduced from 4,857 to 1,782 and the number of CRC deaths from 1,393 to 457, while saving CAN$68 per person. Although screening patients with FIT became more expensive than a strategy of no screening when the test performance of FIT was reduced, or the cost of managing CRC was lowered (e.g., for jurisdictions that do not fund expensive biologic chemotherapeutic regimens), CRC screening with FIT remained economically attractive.

Conclusions

CRC screening with FIT reduces the risk of CRC and CRC-related deaths, and lowers health care costs in comparison to no screening and to other existing screening strategies. Health policy decision makers should consider prioritizing funding for CRC screening using FIT.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Colorectal (bowel) cancer is the second leading cause of cancer deaths for both men and women in North America. Colorectal cancer screening is an important means for reducing morbidity and mortality and fulfils the World Health Organization criteria for mass screening. However, a variety of CRC screening approaches are available. Colonoscopy is viewed as the gold standard of colorectal cancer screening as it has a high sensitivity for identifying adenomas and cancer and polyps can be removed during the screening examination. However, colonoscopy is associated with a number of complications and there are also barriers to access. Another type of test, the guaiac fecal occult blood test, has been shown to reduce mortality from colorectal cancer but this test has low sensitivity for identifying colorectal neoplasia, particularly adenomas. Fecal immunochemical tests, which also detect blood in the stool, have improved test performance characteristics (high sensitivity and specificity) and the potential to improve participation rates compared to guaiac fecal occult blood test and flexible sigmoidoscopy. Fecal DNA (a stool test, based on the detection of DNA shed by cancerous tissue) is another screening option, as is computed tomographic colonography (“virtual” colonoscopy), that might rival colonoscopy in detecting advanced adenomas and colorectal cancer but is expensive and requires a full colonic preparation.

Why Was This Study Done?

In the absence of firm comparative evidence to guide the selection of any one screening modality and given the varied test performance characteristics and the significant differences in costs and resources associated with each, a robust cost-effectiveness analysis might help health policy makers in deciding whether or not to offer screening and if so, in selecting the most appropriate and cost effective screening modality. In this study the researchers conducted a full economic evaluation of all relevant colorectal cancer screening modalities in North America.

What Did the Researchers Do and Find?

The researchers used an incremental cost-utility analysis, a sophisticated modeling technique, and two hypothetical patient cohorts (individuals with an “average risk,” i.e., no family history of colorectal cancer, aged 50–64 and 65–75) to compare guaiac-based fecal occult blood test or fecal immunochemical test annually (the researchers considered three distinct fecal immunochemical testing strategies on the basis of assays and collection methods taken from studies that have reported “low,” “mid,” and “high” test performance characteristics), fecal DNA every three years, flexible sigmoidoscopy or computed tomographic colonography every 5 years, and colonoscopy every 10 years. The researchers also included a no screening natural history arm as a comparison to each screening approach. For the baseline data of their model, the researchers used adenoma and colorectal prevalence rates from a recent systematic review and based screening adherence, test performance, and colorectal treatment costs on available data. The researchers found that annual fecal immunochemical testing with mid-range testing characteristics, was more effective and less costly compared to all strategies (including no screening). Using this screening modality, among the lifetimes of 100,000 average-risk patients, the number of cancers could be reduced from 4,857 to 1,393 and the number of deaths from colorectal cancer from 1,782 to 457, while saving CAN$68 per person. Although in the sensitivity and scenario analysis, screening patients using fecal immunochemical testing became more expensive than a strategy of no screening when the test performance of fecal immunochemical testing was reduced, or the cost of managing colorectal cancers was lowered, the researchers found that screening for colorectal cancer with fecal immunochemical testing remained the most economically attractive screening option.

What Do These Findings Mean?

This model-based economic analysis found that fecal immunochemical testing is more effective and less costly than all other colorectal screening strategies, including the most commonly-used stool-based screening test, guaiac-based fecal occult blood testing, and no screening. Furthermore, this study suggests that annual screening with fecal immunochemical testing (assuming mid-range test performance characteristics) reduces the risk of colorectal cancer and colorectal cancer–related deaths, and lowers health care costs in comparison to all other screening strategies and to no screening. Therefore, health policy makers should consider prioritizing funding for fecal immunochemical testing as the screening modality for colorectal cancer.

Additional Information

Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000370.

Cancer.org has information for patients on colorectal cancer

The US Centers for Disease Control (CDC) list colorectal screening guidelines

The CDC also provides patient information on colorectal cancer Screening

Background

HPV burden is a predictor for high-grade cervical intraepithelial neoplasia and cancer. The natural history of HPV load in young women being recently exposed to HPV is described in this paper.

Methods

A total of 636 female university students were followed for 2 years. Cervical specimens with HPV-16, -18, -31, or -45 DNA by consensus PCR were further evaluated with type-specific and β-globin real-time PCR assays. Proportional hazards regression was used to estimate hazard ratios (HR) of infection clearance. Generalized estimating equations assessed whether HPV loads was predictive of HPV infection at the subsequent visit.

Results

HPV loads were consistently higher among women <25 years old, and those who had multiple sex partners, multiple HPV type infections and smokers. HPV-16 integration was encountered only in one sample. Infection clearance was faster among women at lower tertiles of HPV-16 (HR = 2.8, 95%CI: 1.0-8.1), HPV-18 (HR = 3.5, 95%CI: 1.1-11.2) or combined (HR = 2.4, 95%CI: 1.8-6.2) DNA loads. The relationship between HPV-16 and HPV-18 DNA loads and infection clearance followed a clear dose-response pattern, after adjusting for age and number of sexual partners. GEE Odds Ratios for HPV persistence of the middle and upper tertiles relative to the lower tertile were 2.7 and 3.0 for HPV-16 and 3.8 and 39.1 for HPV-18, respectively. There was no association between HPV-31 or -45 DNA loads and persistence.

Conclusions

The association between HPV load and persistence is not uniform across high-risk genital genotypes. HPV-16 integration was only rarely demonstrated in young women.

Eduardo Franco and Guy-Anne Turgeon discuss new findings from Joel Ray and colleagues on the cancer risk following prenatal exposure to radiodiagnostic imaging, and where new research needs to be focused.

In a record-linkage study, Joel Ray and colleagues examine the association between diagnostic imaging during pregnancy and later childhood cancers.

Background

The association between fetal exposure to major radiodiagnostic testing in pregnancy—computed tomography (CT) and radionuclide imaging—and the risk of childhood cancer is not established.

Methods and Findings

We completed a population-based study of 1.8 million maternal-child pairs in the province of Ontario, from 1991 to 2008. We used Ontario's universal health care–linked administrative databases to identify all term obstetrical deliveries and newborn records, inpatient and outpatient major radiodiagnostic services, as well as all children with a malignancy after birth. There were 5,590 mothers exposed to major radiodiagnostic testing in pregnancy (3.0 per 1,000) and 1,829,927 mothers not exposed. The rate of radiodiagnostic testing increased from 1.1 to 6.3 per 1,000 pregnancies over the study period; about 73% of tests were CT scans. After a median duration of follow-up of 8.9 years, four childhood cancers arose in the exposed group (1.13 per 10,000 person-years) and 2,539 cancers in the unexposed group (1.56 per 10,000 person-years), a crude hazard ratio of 0.69 (95% confidence interval 0.26–1.82). After adjusting for maternal age, income quintile, urban status, and maternal cancer, as well as infant sex, chromosomal or congenital anomalies, and major radiodiagnostic test exposure after birth, the risk was essentially unchanged (hazard ratio 0.68, 95% confidence interval 0.25–1.80).

Conclusions

Although major radiodiagnostic testing is now performed in about 1 in 160 pregnancies in Ontario, the absolute annual risk of childhood malignancy following exposure in utero remains about 1 in 10,000. Since the upper confidence limit of the relative risk of malignancy may be as high as 1.8 times that of an unexposed pregnancy, we cannot exclude the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

In industrialized countries, childhood cancer (any form of cancer in a child aged 14 years or under) remains a major cause of death. With the exception of a few known risk factors, such as acquired genetic predisposition to cancer, which accounts for about 10% of all childhood cancers, the etiology of most childhood cancer remains unknown. There is thought to be an association between exposure to ionizing radiation in pregnancy and the subsequent risk of development of cancer in the exposed mother's child, but the evidence base to support this association is conflicting. For example, studies examining maternal exposure to plain radiographs in pregnancy and subsequent childhood cancer are inconsistent. Furthermore, although their use has dramatically increased over the past two decades, little is known about the cancer risk related to certain types of radiodiagnostic tests, such as CT and radionuclide imaging, both of which expose the fetus to considerably higher doses of radiation than plain radiographs administered at the same anatomical level.

Why Was This Study Done?

Many women could be exposed to major radiodiagnostic tests, such as those used in emergency situations, before they are aware that they are pregnant, as almost 50% of pregnancies are unplanned. This situation means that it is important to determine the subsequent cancer risk to any child exposed to maternal radiodiagnostic tests before birth.

What Did the Researchers Do and Find?

The researchers conducted a retrospective population-based cohort study of women who delivered a live infant in Ontario, Canada between April 1, 1992 and March 31, 2008. The basis of the research was an anonymized database for the whole province of Ontario, where universal health care, including prenatal care and radiodiagnostic testing, is available to all residents. Database characteristics allowed the researchers to link maternal radiation exposure (a major radiodiagnostic test performed on the mother up to one day before her delivery date) in a specific (index) pregnancy to a subsequent malignancy in the child. After birth, maternal-infant pairs were only followed up if the infant was delivered at term, weighed 2,500 g or more, and survived for at least 30 days.

The researchers were able to follow up 1,835,517 maternal-child pairs. The overall rate of exposure to major radiodiagnostic testing in pregnancy was 3.0 per 1,000 and occurred at an estimated mean gestational age of 15.7 weeks. A total of four childhood cancers occurred in the exposed group and 2,539 cancers in the unexposed group corresponding to a crude hazard ratio of 0.69, which did not significantly change after adjustments were made for potential confounding factors, such as maternal age, sex, and the presence of any chromosomal or congenital anomalies in the infant. The overall prevalence of childhood cancer following exposure to CT or radionuclide imaging in pregnancy is under 0.07%, giving an incidence rate of 1.13 per 10,000 person-years.

What Do These Findings Mean?

These findings can help inform clinicians and mothers about the risk of childhood malignancy following major radiodiagnostic testing in pregnancy. The absolute risk appears to be low, while the relative risk is not materially higher than that of unexposed controls. However, as the upper confidence limit of the relative risk of malignancy may be a maximum of 1.8 times that of an unexposed pregnancy, the possibility that fetal exposure to CT or radionuclide imaging is carcinogenic cannot be excluded. Because this finding means that a very slight risk may exist, beta hCG testing should continue to be done in all potentially pregnant women before undergoing major radiodiagnostic testing, and lead apron shielding used in all women of reproductive age, whether or not known to be pregnant. In addition, nonradiation-emitting imaging, such as MRI and ultrasonography, should be considered first, when clinically appropriate. However, some pregnant women will still be faced with the decision to undergo CT or nuclear imaging because the test is clinically warranted. The findings of this study suggest that when clinically indicated, major radiodiagnostic testing in pregnancy should be performed, along with brief counseling to help lessen the anxiety experienced by an expectant mother before and after the birth of her child.

Additional Information

Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1000337.

For information for patients and caregivers on radiodiagnostic testing, see The Royal College of Radiologists

The National Cancer Institute provides information about childhood cancer

CureSearch for Children's Cancer provides additional information about research into childhood cancer

The serological detection of antibodies against human papillomavirus (HPV) antigens is a useful tool to determine exposure to genital HPV infection and in predicting the risk of infection persistence and associated lesions. Enzyme-linked immunosorbent assays (ELISAs) are commonly used for seroepidemiological studies of HPV infection but are not standardized. Intra- and interassay performance variation is difficult to control, especially in cohort studies that require the testing of specimens over extended periods. We propose the use of normalized absorbance ratios (NARs) as a standardization procedure to control for such variations and minimize measurement error. We compared NAR and ELISA optical density (OD) values for the strength of the correlation between serological results for paired visits 4 months apart and HPV-16 DNA positivity in cervical specimens from a cohort investigation of 2,048 women tested with an ELISA using HPV-16 virus-like particles. NARs were calculated by dividing the mean blank-subtracted (net) ODs by the equivalent values of a control serum pool included in the same plate in triplicate, using different dilutions. Stronger correlations were observed with NAR values than with net ODs at every dilution, with an overall reduction in nonexplained regression variability of 39%. Using logistic regression, the ranges of odds ratios of HPV-16 DNA positivity contrasting upper and lower quintiles at different dilutions and their averages were 4.73 to 5.47 for NARs and 2.78 to 3.28 for net ODs, with corresponding significant improvements in seroreactivity-risk trends across quintiles when NARs were used. The NAR standardization is a simple procedure to reduce measurement error in seroepidemiological studies of HPV infection.

Background

Mutations in TP53 are common events during carcinogenesis. In addition to gene mutations, several reports have focused on TP53 polymorphisms as risk factors for malignant disease. Many studies have highlighted that the status of the TP53 codon 72 polymorphism could influence cancer susceptibility. However, the results have been inconsistent and various methodological features can contribute to departures from Hardy-Weinberg equilibrium, a condition that may influence the disease risk estimates. The most widely accepted method of detecting genotyping error is to confirm genotypes by sequencing and/or via a separate method.

Results

We developed two new genotyping methods for TP53 codon 72 polymorphism detection: Denaturing High Performance Liquid Chromatography (DHPLC) and Dot Blot hybridization. These methods were compared with Restriction Fragment Length Polymorphism (RFLP) using two different restriction enzymes. We observed high agreement among all methodologies assayed. Dot-blot hybridization and DHPLC results were more highly concordant with each other than when either of these methods was compared with RFLP.

Conclusions

Although variations may occur, our results indicate that DHPLC and Dot Blot hybridization can be used as reliable screening methods for TP53 codon 72 polymorphism detection, especially in molecular epidemiologic studies, where high throughput methodologies are required.