Effect of ethnicity on first trimester biomarkers for combined trisomy 21 screening: results from a multicenter study in six Asian countries.

OBJECTIVE: To assess differences between first trimester trisomy 21 screening markers free beta chain of the human chorionic gonadotrophin (ßhCG) and pregnancy-associated plasma protein A (PAPP-A) in pregnant women of six different Asian countries (China, Indonesia, Korea, Taiwan, Thailand, and Vietnam) and compare serum levels with those in women of European countries. METHODS: Median and multiple of median (MoM) values of free ßhCG and PAPP-A were determined in more than 3000 pregnant women from the Asian countries during their first trimester of pregnancy. Differences in MoM values between a European reference group from a previous multicenter evaluation and the Asian population were evaluated. Two different types of population correction factors for T21 risk estimation were assessed. RESULTS: An at least 10% difference of median MoMs between European and Asian PAPP-A values was found to be statistically significant (p < 0.0001). The specificity of the screening did not show a big difference in individual countries, when using the country-specific correction factor compared with the overall Asian correction factor (<1.4%). CONCLUSIONS: The use of a correction factor is recommended based on the differences in European and Asian MoM values. Developing country-specific medians in larger study populations can help identify clinical relevant differences and give the opportunity to explore a more accurate risk calculation.