Second Trimester Prenatal Screening for Down’s Syndrome in Mainland Chinese Subjects using Double-Marker Analysis of α-fetoprotein and β-human Chorionic Gonadotropin Combined with Measurement of Nuchal Fold Thickness

Abstract

Introduction: This study examines the effectiveness of double-marker analysis for α-fetoprotein (AFP) and β-human chorionic gonadotropin (β-hCG) combined with measurement of nuchal fold thickness (NT) in the detection of Down’s syndrome (DS) in Mainland Chinese subjects during second trimester prenatal screening. Materials and Methods: We examined pregnant women with a singleton pregnancy between 15 and 21 weeks of gestation who underwent second trimester screening for DS using double-marker analysis for AFP and β-hCG combined with ultrasound measurement of NT. The combined risk of DS was calculated. A cut-off of 1/270 was used to defi ne a pregnancy at high-risk of DS. Amniocentesis was offered to all patients with high-risk pregnancies. Results: Using double-marker analysis for AFP and β-hCG in combination with measurement of NT, the detection rate of DS increased from 66.7% to 77.8% when compared with double-marker analysis alone with similar false-positive rates (4.35%, 4.83% respectively). Using receiver operating characteristic curve (ROC) analysis, we determined that the double-marker analysis combined with measurement of NT exhibited an increased area under the curve (AUC) of 0.835 (95% CI: 0.743 to 0.927) when compared to double-marker analysis alone, which had an AUC of 0.748 (95% CI: 0.635 to 0.860). In addition, both methods were more effective than any other single test such as AFP, free β-hCG or NT measurement. Conclusion: Second trimester prenatal screening using double-marker analysis for AFP and β-hCG combined with measurement of NT is effective for the detection of DS in Mainland Chinese pregnancies. Key words: Down’s syndrome, Prenatal screening, Second trimester