A new contingent screening strategy increased detection rate of trisomy 21 in the first trimester

BackgroundAlthough the traditional contingent screening strategy is effective, there are still undetected low-risk trisomy 21. This study aims to define appropriate cut-off values of serum biochemical markers at low-risk and develop a strategy for sequential prenatal testing associated with first-trimester screening to increase the detection rate of trisomy 21.MethodsThis was a 9-year retrospective analysis of singleton pregnant women who underwent serum biochemical screening or combined first-trimester screening (CFTS) in the first trimester. For the low-risk group, the cut-off values of the serum biochemical markers were adjusted to determine the appropriate detection efficiency. Gravidas with abnormal serum biochemical markers at low-risk were advised to undergo further non-invasive prenatal screening (NIPS), whereas others continued with routine prenatal care.ResultsWhen cut-off values of free beta subunit of human chorionic gonadotropin (free beta-hCG) multiples of the median (MoM) or pregnancy-associated plasma protein A (PAPP-A) MoM were defined with >= 2.75 or <= 0.5, 7.72% (2,194/28,405) in the serum biochemical screening group and 12.36% (4,005/32,403) in CFTS group could be detected as abnormal results for further NIPS. Finally, 55.56% (5/9) and 85.71% (6/7) of trisomy 21 cases with false-negative results were detected, and the overall detection rate for trisomy 21 was improved by 10.64% (5/47) and 12.77% (6/47), respectively.ConclusionsThe new contingent screening strategy can increase the detection rate of trisomy 21 compared with the traditional contingent screening strategy.

Automated summary

The study aims to increase the detection rate of trisomy 21 by defining appropriate cut-off values of serum biochemical markers and developing a sequential prenatal testing strategy associated with first-trimester screening. The results demonstrate that the new contingent screening strategy has a higher detection rate compared to the traditional strategy.