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Predictive genetic testing for the identification of high-risk groups: a simulation study on the impact of predictive ability.

ABSTRACT: BACKGROUND: Genetic risk models could potentially be useful in identifying high-risk groups for the prevention of complex diseases. We investigated the performance of this risk stratification strategy by examining epidemiological parameters that impact the predictive ability of risk models. METHODS: We assessed sensitivity, specificity, and positive and negative predictive value for all possible risk thresholds that can define high-risk groups and investigated how these measures depend on the frequency of disease in the population, the frequency of the high-risk group, and the discriminative accuracy of the risk model, as assessed by the area under the receiver-operating characteristic curve (AUC). In a simulation study, we modeled genetic risk scores of 50 genes with equal odds ratios and genotype frequencies, and varied the odds ratios and the disease frequency across scenarios. We also performed a simulation of age-related macular degeneration risk prediction based on published odds ratios and frequencies for six genetic risk variants. RESULTS: We show that when the frequency of the high-risk group was lower than the disease frequency, positive predictive value increased with the AUC but sensitivity remained low. When the frequency of the high-risk group was higher than the disease frequency, sensitivity was high but positive predictive value remained low. When both frequencies were equal, both positive predictive value and sensitivity increased with increasing AUC, but higher AUC was needed to maximize both measures. CONCLUSIONS: The performance of risk stratification is strongly determined by the frequency of the high-risk group relative to the frequency of disease in the population. The identification of high-risk groups with appreciable combinations of sensitivity and positive predictive value requires higher AUC.

SUBMITTER: Mihaescu R

PROVIDER: S-EPMC3221548 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Predictive genetic testing for the identification of high-risk groups: a simulation study on the impact of predictive ability.

Mihaescu Raluca R Moonesinghe Ramal R Khoury Muin J MJ Janssens A Cecile Jw AC

Genome medicine 20110728 7

<h4>Background</h4>Genetic risk models could potentially be useful in identifying high-risk groups for the prevention of complex diseases. We investigated the performance of this risk stratification strategy by examining epidemiological parameters that impact the predictive ability of risk models.<h4>Methods</h4>We assessed sensitivity, specificity, and positive and negative predictive value for all possible risk thresholds that can define high-risk groups and investigated how these measures dep ...[more]

PMID: 21797996

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Project description:This multi-centre UK study assesses the impact of predictive testing for breast and ovarian cancer predisposition genes (BRCA1/2) in the clinical context. In the year following predictive testing, 261 adults (59 male) from nine UK genetics centres participated; 91 gene mutation carriers and 170 noncarriers. Self-report questionnaires were completed at baseline (pre-genetic testing) and 1, 4 and 12 months following the genetic test result. Men were assessed for general mental health (by general health questionnaire (GHQ)) and women for general mental health, cancer-related worry, intrusive and avoidant thoughts, perception of risk and risk management behaviour. Main comparisons were between female carriers and noncarriers on all measures and men and women for general mental health. Female noncarriers benefited psychologically, with significant reductions in cancer-related worry following testing (P<0.001). However, younger female carriers (<50 years) showed a rise in cancer-related worry 1 month post-testing (P<0.05). This returned to pre-testing baseline levels 12 months later, but worry remained significantly higher than noncarriers throughout (P<0.01). There were no significant differences in GHQ scores between males and females (both carriers and noncarriers) at any time point. Female carriers engaged in significantly more risk management strategies than noncarriers in the year following testing (e.g. mammograms; 92% carriers vs 30% noncarriers). In the 12 months post-testing, 28% carriers had bilateral risk-reducing mastectomy and 31% oophorectomy. Oophorectomy was confined to older (mean 41 yrs) women who already had children. However, worry about cancer was not assuaged by surgery following genetic testing, and this requires further investigation. In all, 20% of female carriers reported insurance problems. The data show persistent worry in younger female gene carriers and confirm changes in risk management consistent with carrier status. Men were not adversely affected by genetic testing in terms of their general mental health.

Project description:Hereditary nonpolyposis colorectal cancer (HNPCC) is frequently associated with constitutional mutations in a class of genes involved in DNA mismatch repair. We identified 32 kindreds, with germline mutations in one of three genes hMSH2, hMLH1 or hMSH6. In this study, we purposed to evaluate how many high-risk individuals in each family underwent genetic testing: moreover, we assessed how many mutation-positive unaffected individuals accepted colonoscopic surveillance and the main findings of the recommended follow-up. Families were identified through a population-based registry, or referred from other centres. Members of the families were invited for an education session with two members of the staff. When a kindred was consistent with HNPCC, neoplastic tissues were examined for microsatellite instability (MSI) and immunohistochemical expression of MSH2, MLH1 and MSH6 proteins. Moreover, constitutional mutations were searched by SSCP or direct sequencing of the whole genomic region. Of the 164 subjects assessed by genetic testing, 89 were gene carriers (66 affected - that is, with HNPCC-related cancer diagnosis - and 23 unaffected) and 75 tested negative. Among the 23 unaffected gene carriers, 18 (78.3%) underwent colonoscopy and four declined. On a total of 292 first degree at risk of cancer, 194 (66.4%) did not undergo genetic testing. The main reasons for this were: (a) difficulty to reach family members at risk, (b) lack of collaboration, (c) lack of interest in preventive medicine or 'fatalistic' attitude towards cancer occurrence. The number of colorectal lesions detected at endoscopy in gene carriers was significantly (P<0.01) higher than in controls (noncarriers). We conclude that a large fraction of high-risk individuals in mutation-positive HNPCC families does not undergo genetic testing, despite the benefits of molecular screening and endoscopic surveillance. This clearly indicates that there are still barriers to genetic testing in HNPCC, and that we are unable to provide adequate protection against cancer development in these families.

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Predictive genetic testing for the identification of high-risk groups: a simulation study on the impact of predictive ability.

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Predictive genetic testing for the identification of high-risk groups: a simulation study on the impact of predictive ability.

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