FMR1 premutation frequency in a large, ethnically diverse population referred for carrier testing.

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and is caused by an expansion of cytosine-guanine-guanine (CGG) repeats in the FMR1 gene. Female premutation allele carriers (55-200 CGG repeats) are at risk to have an affected child. Currently, specific population-based carrier screening for FXS is not recommended. Previous studies exploring female premutation carrier frequency have been limited by size or ethnicity. This retrospective study provides a pan-ethnic estimate of the Fragile X premutation carrier frequency in a large, ethnically diverse population of women referred for routine carrier screening during a specified time period at Progenity, Inc. Patient ethnicity was self-reported and categorized as: African American, Ashkenazi Jewish, Asian, Caucasian, Hispanic, Native American, Other/Mixed/Unknown, or Sephardic Jewish. FXS test results were stratified by ethnicity and repeat allele category. Total premutation carrier frequency was calculated and compared against each ethnic group. A total of 134,933 samples were included. The pan-ethnic premutation carrier frequency was 1 in 201. Only the Asian group differed significantly from this frequency. Using the carrier frequency of 1 in 201, a conservative pan-ethnic risk estimate for a male fetus to have FXS can be calculated as 1 in 2,412. This risk is similar to the highest ethnic-based fetal risks for cystic fibrosis and spinal muscular atrophy, for which population-wide screening is currently recommended. This study adds to the literature and supports further evaluation into specific population-wide screening recommendations for FXS.

Clinical experience with multigene carrier panels in the reproductive setting.

OBJECTIVES: Expanded carrier testing is acknowledged as an acceptable strategy for carrier testing by the American College of Obstetrics and Gynecology. Limited studies have investigated positivity rates of expanded carrier panels. We describe our experience with 3 commercial laboratory panels varying in size from 3 to 218 disorders. METHODS: We reviewed outcomes for 3 multigene carrier screening panels: trio (3 diseases), standard (23 diseases), and global (218 diseases). All panels used targeted genotype analysis of preselected mutations via next-generation sequencing. We calculated positivity rates for each panel. RESULTS: Positivity rates were 7.2% for Preparent Trio, 13.2% for Preparent Standard, and 35.8% for Preparent Global. The most frequent positive results in the global panel were (in descending order): abnormal hemoglobin electrophoresis, familial Mediterranean fever, cystic fibrosis, fragile X, glucose-6-phosphate dehydrogenase deficiency, alpha-thalassemia, and nonsyndromic hearing loss. CONCLUSIONS: While genetic diseases are individually rare, they are cumulatively common. Our experience illustrates that, with a panel of 218 diseases, the likelihood of identifying a carrier can be as high as 36%. Understanding panel positivity rates is one important factor for providers when choosing the right test for their practice, setting appropriate expectations for patients, and planning for follow-up counseling.

To reflex or not: additional BRCA1/2 testing in Ashkenazi Jewish individuals without founder mutations.

This study determined the prevalence of non-Ashkenazi Jewish BRCA1/2 mutations in the Ashkenazi Jewish population in the state of Michigan, current provider testing practices, and the use of mutation probability models in determining which Ashkenazi Jewish individuals should be offered further analysis following negative BRCA1/2 founder testing. Testing patterns, mutation probabilities, and testing results were assessed for 327 Ashkenazi Jewish individuals seen for BRCA1/2 counseling in the state of Michigan who underwent testing for the Ashkenazi Jewish founder mutations. Only one (0.6 %) Ashkenazi Jewish individual with sequencing after negative founder analysis was found to have a non-founder mutation; no rearrangements were identified. Testing patterns varied by clinic, with the proportion of Ashkenazi Jewish individuals undergoing additional sequencing ranging from 22.2 to 92.9 %. In Ashkenazi Jewish individuals with a pre-test BRCAPRO risk calculation, the mean risk was significantly higher in those with follow-up sequencing compared to those who did not pursue additional testing. The low prevalence of non-founder BRCA1/2 mutations in Ashkenazi Jewish individuals does not warrant automatically reflexing to full analysis after negative mutation testing. Increased use of mutation probability models may aid in determining which cases warrant additional testing.

Psychological distress with direct-to-consumer genetic testing: a case report of an unexpected BRCA positive test result.

We report a case of a client who discovered she had a BRCA mutation following direct-to-consumer (DTC) genetic testing in the absence of genetic counseling. After testing she presented for genetic counseling with anxiety, distress, and a deficit of knowledge about what the DTC genetic testing revealed. Genetic counseling helped alleviate distress while empowering the client to apply the results of testing to improve medical management. Despite recent studies demonstrating no negative psychological impact of DTC genetic testing on the consumer, this case illustrates that significant psychological distress and confusion can occur as a result of DTC genetic testing for highly penetrant single gene disorders. Pre- and post-test genetic counseling in conjunction with DTC genetic testing may alleviate consumers' distress and empower clients to proactively utilize their result information.

Errors in delivery of cancer genetics services: implications for practice.

UNLABELLED: Advances in genetics have prompted recommendations that all healthcare providers perform genetic counseling and testing. Some experts are concerned about potential negative outcomes from cancer genetic testing performed without genetic counseling by certified genetics professionals. We report a national series of cases illustrating negative outcomes of cancer genetic testing performed without counseling by a qualified provider. Three major patterns emerged from analysis of these cases: 1) Wrong genetic test ordered, 2) Genetic test results misinterpreted, and 3) Inadequate genetic counseling. Negative outcomes included unnecessary prophylactic surgeries, unnecessary testing, psychosocial distress, and false reassurance resulting in inappropriate medical management. CONCLUSION: With the complexities of cancer genetic counseling and testing, it may be unrealistic to expect all clinicians to provide these services. A more realistic approach is better provider education and a framework in which healthcare providers identify patients who would benefit from a referral to a certified genetic counselor or experienced cancer genetics professional.