Diagnostic Testing Uptake After High-Risk cffDNA Results for Sex Chromosome Aneuploidy [11B

Abstract

INTRODUCTION: The phenotype of sex chromosome aneuploidy (SCA) is typically mild, except in fetuses with cystic hygroma/hydrops. We hypothesize that because the phenotype of SCA is variable, the uptake of diagnostic testing after positive cffDNA screening varies between different SCA. Our study aim was to describe the uptake of diagnostic testing after a positive cffDNA screen for SCA. METHODS: A retrospective study of singleton gestations and abnormal cffDNA results for 45,X, 47,XXY or other SCA from 10/2012 to 3/2016. Any unreportable and other positive cffDNA results were excluded. Based on cffDNA results, 3 cohorts were defined: high-risk for 45,X, 47,XXY or other SCA. Diagnostic testing was offered to all study subjects. Primary outcome was uptake rate of diagnostic testing by abnormal cffDNA SCA results in 3 groups. P-value of < .05 was considered significant. RESULTS: 109 women met inclusion criteria. Demographics were similar in the 3 groups. The overall uptake of diagnostic testing after abnormal cffDNA for SCA was 22.9%. It was higher in 45,X cohort (36.7%) compared to 47,XXY (14.3%); none of the patients in “other SCA” cohort accepted diagnostic testing (P=.0004). The false positive and confirmation rate of suspected chromosomal abnormality was similar in 45,X and 47,XXY group (P=.68). CONCLUSION: Only 23% of women with positive cffDNA for SCA proceed with diagnostic testing. Of all SCA, the uptake is noted to be highest for 45,X. The increased uptake in 45,X may be due to a higher likelihood of abnormal ultrasound findings such as cystic hygroma. Further analysis of this observation is indicated.