OC05.10: Genetic results in nuchal translucency above the 99th percentile

Abstract

Oral communication abstractsResults: After exclusions, 18,299 pregnancies were available for analysis [BJ1] [KAM2]. Seven cases of 45,X were confirmed in the cohort including 4 with mosaicism, for a prevalence of 1:2614. cfDNA identified 6/7 cases (sensitivity=85.7%). cfDNA results reported high risk for 45,X in 24 cases; 6 of these were confirmed (PPV=25.0%). The updated algorithm did not return a result in 1 affected case, the sensitivity and PPV did not significantly change (83.3% and 33.3%). In 4/7 cases discordance was noted between confirmatory diagnostic tests, summarised in table 1. Conclusions: The prevalence of 45,X was 1:2614, consistent with historical data. The sensitivity of cfDNA was high, despite 4/7 cases with mosaicism. The high rate of discordance between diagnostic tests challenges providers to re-evaluate guidelines for evaluation of high risk cfDNA results for 45,X.