Contingent triple-screening for Down syndrome in the second trimester: a feasibility study in Mainland Chinese population.

Objectives: To explore the efficacy of contingent triple-screening for Down syndrome (DS), that is, performing triple-screening in pregnant women with DS risks between 1/270 and 1/1000 at routine double-screening, in a Mainland Chinese population.

Methods: Maternal serum concentrations of alpha fetoprotein (AFP), free-beta human chorionic gonadotropin (free beta-hCG), and unconjugated estriol (uE3) were measured by time-resolved fluoroimmunoassay in 24 double-screening false-negative (DSFN) and 322 double-screening true-negative (DSTN) pregnancies with DS risks between 1/270 and 1/1000 at routine double-screening performed at 15-20 weeks' gestation. DS risk of each pregnancy was calculated by computer software. The detection rate (DR), false-positive rate (FPR), and costs of contingent triple-screening were calculated and compared with routine double-screening methods.

Results: Six of 24 DSFN and 3 of 322 DSTN were contingent triple-screening positive. Compared with routine double-screening, DR of contingent triple-screening increased by 10% (from 50% to 60%) without a significant increase of FPR (p > 0.05). When compared with routine triple-screening, uE3 costs in contingent triple-screening were reduced by more than 84.3%.

Conclusions: Second-trimester maternal serum contingent triple-screening could be effective and suitable for prenatal care in Mainland China. Governments and Health Agencies of other developing countries may also find this strategy cost-effective.