Monica R. McClain

EGAPP supplementary evidence review: DNA testing strategies aimed at reducing morbidity and mortality from Lynch syndrome

1. Clarifying how to define the clinical disorder—Lynch syndrome. In this supplementary review, Lynch syndrome refers to individuals with a predisposition to CRC and certain other malignancies as a result of a germline mismatch repair (MMR) gene mutation—including those with an existing cancer and those who have not yet developed cancer. This definition allows planned analyses of clinical validity and utility to be more straightforward. Several recent editorials and publications recommend that the ambiguous term HNPCC be abandoned and that this clarified definition of Lynch syndrome should be used instead. 2. Removing family history from consideration as a preliminary test. A previous evidence review showed that screening performance of both the Amsterdam and the Bethesda criteria to identify individuals with Lynch syndrome were highly heterogeneous, possibly due to differences among the populations tested. In a general population, Amsterdam criteria are associated with relatively low sensitivity (28‐45%), but high specificity (99%), whereas Bethesda criteria are associated with higher sensitivity (73‐91%), but at the cost of lower specificity (82‐77%). Neither provides the necessary high sensitivity/specificity in a reliable and consistent manner. There are also gaps in knowledge relating to the time required to

First- and second-trimester thyroid hormone reference data in pregnant women: a FaSTER (First- and Second-Trimester Evaluation of Risk for aneuploidy) Research Consortium study

OBJECTIVE The purpose of this study was to calculate first and second trimester reference ranges and within-woman correlations for TSH, free T4, and thyroid antibodies. STUDY DESIGN TSH, free T4, and thyroid antibodies were measured in paired sera from 9562 women in the FaSTER trial of Down syndrome screening. RESULTS The median first trimester TSH (1.05 mIU/L) is lower than the second (1.23 mIU/L); and 98th centile is higher (4.15 vs 3.77 mIU/L). Within-woman paired TSH correlations are moderately strong (r(2) = 0.64). Among women with first trimester TSH values above the 98th centile, second trimester values are over the 95th centile in 68%. Median first trimester free T4 values (1.10 ng/dL) are higher than second (1.01 ng/dL). Paired free T4 measurements correlate weakly (r(2) = 0.23). Among women with first trimester free T4 values below the 2nd centile, second trimester values are below the 5th centile in 32%. Antibody measurements correlate strongly between trimesters (thyroperoxidase r(2) = 0.79, thyroglobulin r(2) = 0.83). CONCLUSION TSH and free T4 measurements require gestation-specific reference ranges.

A Rapid-ACCE review of CYP2C9 and VKORC1 alleles testing to inform warfarin dosing in adults at elevated risk for thrombotic events to avoid serious bleeding

Purpose: Summarize evidence regarding genetic testing in adults to inform warfarin dosing to reduce adverse drug events such as serious bleeding.Methods: Review published (and selected gray) literature using the Rapid-ACCE structure that addresses analytic validity, clinical validity, clinical utility, and ethical, legal, and social implications.Results: Preliminary data suggest overall analytic sensitivity and specificity will be 98% or higher for CYP2C9 genotyping, but strength of evidence for analytic validity is low, especially for VKORC1 testing. Strength of evidence is high for the clinical validity of both genes in predicting stable warfarin dose, an intermediate outcome, but is low for the association between CYP2C9 testing and severe bleeding events (clinical sensitivity 46% (95% CI 32–60%); specificity 69% (95% CI 62–75%) and absent for bleeding events associated with VKORC1 testing. No data are available to document clinical utility of genotyping before warfarin dosing.Conclusions: The most important gaps identified are: which variants should be included in a testing panel, lack of data from external proficiency testing, lack of validated dosing algorithm incorporating genetic and nongenetic factors, evidence of clinical utility, reliable economic analyses, and methods to address several ethical, legal, and social implications issues.

Variability in Thyroid-Stimulating Hormone Suppression by Human Chronic Gonadotropin during Early Pregnancy

OBJECTIVE The objective of the study was to further explore relationships between human chorionic gonadotropin (hCG), TSH, and free T4 in pregnant women at 11 through 18 wk gestation. STUDY DESIGN The design of the study was to analyze hCG in comparison with TSH and free T4, in paired first- and second-trimester sera from 9562 women in the First and Second Trimester Evaluation of Risk for Fetal Aneuploidy trial study. RESULTS hCG is strongly correlated with body mass index, smoking, and gravidity. Correlations with selected maternal covariates also exist for TSH and free T4. As hCG deciles increase, body mass index and percent of women who smoke both decrease, whereas the percent of primigravid women increases (P < 0.0001). hCG/TSH correlations are weak in both trimesters (r2 = 0.03 and r2 = 0.02). TSH concentrations at the 25th and fifth centiles become sharply lower at higher hCG levels, whereas 50th centile and above TSH concentrations are only slightly lower. hCG/free T4 correlations are weak in both trimesters (r2 = 0.06 and r2 = 0.003). At 11-13 wk gestation, free T4 concentrations rise uniformly at all centiles, as hCG increases (test for trend, P < 0.0001), but not at 15-18 wk gestation. Multivariate analyses with TSH and free T4 as dependent variables and selected maternal covariates and hCG as independent variables do not alter these observations. CONCLUSIONS In early pregnancy, a womans centile TSH level appears to determine susceptibility to the TSH being suppressed at any given hCG level, suggesting that hCG itself may be the primary analyte responsible for stimulating the thyroid gland. hCG affects lower centile TSH values disproportionately.

Thyroperoxidase and thyroglobulin antibodies in early pregnancy and preterm delivery.

OBJECTIVE: To further evaluate the relationship between thyroid antibodies and preterm births. METHODS: This is a prospective study of pregnancy outcome and demographic data combined with retrospective measurement of thyroperoxidase and thyroglobulin antibodies. Sera were obtained at 11–13 and 15–18 weeks of gestation from 10,062 women with singleton viable pregnancies (a subset from the First- and Second-Trimester Risk of Aneuploidy [FaSTER] trial). RESULTS: Women with elevated levels of thyroperoxidase, thyroglobulin antibodies, or both in the first trimester have a higher rate of preterm delivery before 37 weeks of gestation than antibody-negative women (7.5% compared with 6.4%, odds ratio [OR] 1.18; 95% confidence interval [CI] 0.95–1.46). This is also the case for very preterm delivery before 32 weeks of gestation (1.2% compared with 0.7%, OR 1.70; 95% CI 0.98–2.94). Preterm premature rupture of membranes is also increased (2.0% compared with 1.2%, OR 1.67; 95% CI 1.05–2.44). These associations are less strong for second-trimester antibody measurements. CONCLUSION: The present data do not confirm strong associations between thyroid antibody elevations and preterm birth found in three of five previously published reports. Preterm premature rupture of membranes appears to contribute to the thyroid antibody-associated early deliveries, possibly as a result of inflammation. LEVEL OF EVIDENCE: II

Adjusting the estimated proportion of breast cancer cases associated with BRCA1 and BRCA2 mutations: Public health implications

Purpose: Mutations in BRCA1 or BRCA2 genes increase breast cancer risk. Assuring reliability of information about these mutations is increasingly important to the health care community; mutation testing is becoming more widespread. We describe a methodology for assessing such information.Methods: Our approach integrates four interdependent epidemiologic parameters: (1) the probability of developing breast cancer, (2) the proportion of breast cancer cases with a BRCA1 or BRCA2 mutation, (3) the proportion of women that carries a mutation, and (4) the proportion of women with a mutation that develops cancer. We assess the plausibility of estimates of these parameters from published reports and commonly accessed information sources.Results: Assuming a fixed probability of developing breast cancer, the following estimates for the other three epidemiologic parameters are derived for women by age 70: 1% to 2% of all breast cancer cases are associated with a BRCA1 or BRCA2 mutation; 1 in 300 to 1 in 465 women carry a mutation; and 35 to 65% of mutation carriers develop breast cancer. Within these ranges, however, only selected combinations are plausible. The proportion of mutation-related breast cancer is lower than listed in some common information sources (1 to 2% vs 6%). Also, penetrance is somewhat lower and the carrier rate somewhat higher.Conclusions: The four epidemiologic parameters can be integrated to test their plausibility. BRCA1 and BRCA2 mutations are associated with only one-third as many breast cancer cases in the general population as reported by commonly accessed information sources.

Rapid ACCE: Experience with a rapid and structured approach for evaluating gene-based testing

Purpose: To present the rapid-ACCE model and report our early experience of using the ACCE structure to guide systematic reviews for the rapid evaluation of emerging genetic tests.Methods: A rapid-ACCE review uses the same 44 questions that were developed for the full-ACCE model to guide the conduct of systematic review. We combined published literature with unpublished data to estimate test performance and input from experts to help clarify qualitative issues. As questions were answered, gaps in knowledge were identified and articulated. The draft review was then sent to outside reviewers whose comments were incorporated into the final document.Results: We conducted two reviews, both of which were completed in 6 months or less (averaging about 100 hours of primary analyst time), within modest budgets. In addition to defining the current state of knowledge about the tests, the identified gaps are expected to help define the research agendas. Both collaborating experts and study sponsors valued both the process and outcomes from the reviews.Conclusions: Based on our early experiences, it is possible to conduct rapid systematic reviews within the ACCE structure of some emerging genetic tests to produce summaries of available evidence and identification of gaps.

Sequential first- and second-trimester TSH, free thyroxine, and thyroid antibody measurements in women with known hypothyroidism: a FaSTER trial study

OBJECTIVE The purpose of this study was to examine how closely hypothyroidism management in the general pregnancy population satisfies recently issued guidelines and to determine whether improvements are indicated. STUDY DESIGN This was an observational study in which women at 5 recruitment centers in the first- and second-trimester evaluation of risk for aneuploidy trial allowed the use of sequentially obtained first- and second-trimester sera for additional research. Three hundred eighty-nine women had hypothyroidism by self-report. Thyroid-related measurements were performed on all samples between July 2004 and May 2005. RESULTS Forty-three percent of the thyroid-stimulating hormone (TSH) values are at or above recently recommended guidelines in the first trimester (2.5 mU/L), as opposed to 33% of the values in the second trimester (3.0 mU/L). Twenty percent of the TSH values are at or above a less restrictive 98th percentile of normal in the first trimester, as opposed to 23% of the values in the second trimester. Mean TSH levels are higher in women with antibodies. Free thyroxine values are unremarkable. CONCLUSION Future strategies should focus on more effectively treating women with hypothyroidism who have persistently elevated TSH values.

Screen-positive rates and agreement among six family history screening protocols for breast/ovarian cancer in a population-based cohort of 21- to 55-year-old women

Purpose: Mutations in the BRCA1 and BRCA2 genes are responsible for approximately 2% of breast cancers by age 70 years. Professional and governmental groups recommend using family history protocols as an initial step in identifying women and families for mutation testing. We assess screen-positive rates and levels of agreement between these protocols.Methods: We applied six family history screening protocols to a population-based cohort of 321 women, age 21 to 55 years, who reported their personal and family history of breast and ovarian cancer.Results: The proportion of women and families identified as candidates for mutation testing ranged from 4.4% to 7.8%, depending on the protocol. The protocols had low or fair agreement (kappa <0.75 for 14 of 15 comparisons), but all identified six women (1.9%, 95% confidence interval 0.7%–4.0%) as screen positive. When the effect of missing ages of cancer onset was modeled, these rates increased (range 6.5%–11.5%), and nine women (2.8%) were screen positive by all protocols.Conclusion: Given limitations of family history as a screening test for hereditary cancer related to BRCA1/2 mutations, 1% to 2% of women in the general population should initially be identified for mutation testing. One way to achieve this would be to require that multiple screening protocols agree.

An evaluation of BRCA1 and BRCA2 founder mutations penetrance estimates for breast cancer among Ashkenazi Jewish women

Purpose: Three founder mutations in BRCA1 or BRCA2 genes increase breast cancer risk among Ashkenazi Jewish women. Reported estimates of the magnitude of this risk vary widely. We describe an integrated approach for assessing the plausibility of these estimates.Methods: Our approach integrates four epidemiologic parameters: (1) the proportion of all breast cancer cases with a founder mutation, (2) the proportion of women that carry one of these mutations, (3) the proportion of women with a mutation that develops cancer, and (4) the number of women who will develop cancer, regardless of mutation status. We then assess the published estimates of the proportion of Ashkenazi Jewish women with a mutation that develops cancer in the context of the other three parameters.Results: Penetrance for the founder mutations by ages 40, 50, and 70 are approximately 7%, 20%, and 40%, respectively. In two of the four published studies that evaluated at least two of the four parameters, penetrance estimates were internally consistent with the other three parameters and were also consistent with our consensus estimate. The third study had incomplete data. In the fourth study, the penetrance estimate was not internally consistent with the other three parameters, nor was it consistent with the consensus estimate.Conclusions: The four epidemiologic parameters are interdependent and can be used to test the plausibility of any one parameter. Based on the range of breast cancer penetrance estimates for BRCA1 and BRCA2 founder mutations derived by our approach, recently reported penetrance estimates appear to be overestimated.