Applicability of first-trimester combined screening for fetal trisomy 21 in a resource-limited setting in mainland China

Abstract

Objective: To assess the feasibility and performance of the first-trimester combined screening test for trisomy 21 in a resource-limited setting in mainland China. Design: Prospective observational cohort study. Setting: First Affiliated Hospital of Kunming Medical University, China. Population: Ten thousand four hundred and forty-two pregnant women requesting first-trimester screening. Methods: The combined screening test was performed from May 2012 to December 2014. Women with a high-risk result (≥1:600) were offered further confirmatory tests after counselling. The threshold for high risk was determined by Monte Carlo simulation to achieve a 5% false-positive rate according to the local age distribution. Pregnancy outcome and screening results were recorded for all women and monthly audits were conducted. Main outcome measures: Sensitivity, screen positive rate, cost per case of Down syndrome detected. Results: Six hundred and ten women (5.8% of the total screened) had a high-risk screening test, of whom 274 (44.9%) underwent a diagnostic test and 169 (27.7%) opted for a noninvasive prenatal screening test (NIPT); 160 (26.2%) declined further testing after counselling. The pregnancy outcome was available for 10 174 (97.4%) of the women. The observed incidence of Down syndrome was 0.13% (1/750). All 14 women with a trisomy 21 pregnancy had a high-risk screening test result. The cost per Down syndrome detected was RMB596 686 compared with RMB1.79 million if all had been screened by NIPT. Conclusions: The combined screening test appears to be a more cost-effective strategy in mainland China. Screening performance in China would be improved by adopting Chinese-specific models, external quality control and assurance, and establishing risk thresholds appropriate for the age distribution of the population. Tweetable abstract: Combined first-trimester Downs screening in China was improved by adopting Chinese-specific models and external QC.