Results of the College of American Pathology/American College of Medical Genetics and Genomics external proficiency testing from 2006 to 2013 for three conditions prevalent in the Ashkenazi Jewish population

Abstract

The purpose of this study was to determine analytic performance of laboratories offering molecular testing for conditions such as Tay-Sachs disease, Canavan disease, and familial dysautonomia, which are prevalent in the Ashkenazi Jewish population. The College of American Pathologists and the American College of Medical Genetics and Genomics cosponsor molecular proficiency testing for these disorders. Responses from 2006 to 2013 were analyzed for accuracy (genotyping and interpretations). Between 11 and 36 laboratories participated in each Tay-Sachs disease distribution. Samples tested per month were constant (2,900) from 2006 to 2011 but recently increased. Participants reporting <10 samples tested per month had longer turnaround times (42 vs. 7%, longer than 14 days; P = 0.03). Analytic sensitivity and specificity for US participants were 97.2% (95% confidence interval: 94.7-98.7%) and 99.8% (95% confidence interval: 99.1-99.9%), respectively. Of 11 genotyping errors, 2 were due to sample mix-up. Analytic interpretations were correct in 99.3% of challenges (956/963; 95% confidence interval: 98.5-99.7%). Better performance was found for Canavan disease and familial dysautonomia. International laboratories performed equally well. These results demonstrated high analytic sensitivity and specificity along with excellent analytic interpretation performance, confirming the genetics community impression that laboratories provide accurate test results in both diagnostic and screening settings. Proficiency testing can identify potential laboratory issues and helps document overall laboratory performance.