Comparative Diagnostic Testing Uptake and Confirmation Rates After High-Risk cffDNA for Trisomy 21, 18, and 13 [32N

Abstract

INTRODUCTION: There is increasing concern that high-risk cffDNA screening results are not always confirmed by diagnostic testing. We hypothesized that the poorer prognosis of trisomy 18 (T18) or trisomy 13 (T13) compared to trisomy 21 (T21) differentially affects the uptake of confirmatory diagnostic testing after a high-risk cffDNA result for these aneuploidies. METHODS: A retrospective study of singleton gestations with abnormal cffDNA screening for trisomies 21, 18 and 13 between 10/2012 and 3/2016. We excluded multiple gestations, any unreportable and any other positive cffDNA results. Based on cffDNA results, 3 cohorts were compared: high risk for T21, T18 and T13. Diagnostic testing was offered to all study subjects. Primary outcome was uptake rate of diagnostic testing in the 3 groups. A P-value of < 0.05 was considered significant. RESULTS: 278 women met inclusion criteria. Demographics were similar in the 3 groups, except for higher rate of AMA in T21 group compared to T18 and T13 (P=.04). The uptake of diagnostic testing was similar in the 3 groups (P=.79). The confirmation of diagnosis by karyotype or CMA was significantly higher for T21 group compared to T18 and T13 (P=.0001). The rate of false positive cffDNA result was significantly higher in T13 group compared to T18 and T21 (P=.0001). CONCLUSION: There is no difference in uptake of diagnostic testing in women with a cffDNA screening result indicating high risk for Trisomy 21, 18 or 13. Diagnostic testing is more likely to confirm diagnosis of T21 and T18 compared to T13 in women with abnormal cffDNA screening.