Normative weight-adjusted models for the median levels of first trimester serum biomarkers for trisomy 21 screening in a specific ethnicity

OBJECTIVE To establish normative weight-adjusted models for the median levels of first trimester serum biomarkers for trisomy 21 screening in southern Thai women, and to compare these reference levels with Caucasian-specific and northern Thai models. METHODS A cross-sectional study was conducted in 1,150 normal singleton pregnancy women to determine serum pregnancy-associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotropin (β-hCG) concentrations in women from southern Thailand. The predicted median values were compared with published equations for Caucasians and northern Thai women. RESULTS The best-fitting regression equations for the expected median serum levels of PAPP-A (mIU/L) and free β- hCG (ng/mL) according to maternal weight (Wt in kg) and gestational age (GA in days) were: [Formula: see text] and [Formula: see text] Both equations were selected with a statistically significant contribution (p< 0.05). Compared with the Caucasian model, the median values of PAPP-A were higher and the median values of free β-hCG were lower in the southern Thai women. And compared with the northern Thai models, the median values of both biomarkers were lower in southern Thai women. CONCLUSION The study has successfully developed maternal-weight- and gestational-age-adjusted median normative models to convert the PAPP-A and free β-hCG levels into their Multiple of Median equivalents in southern Thai women. These models confirmed ethnic differences.