Higher median levels of free beta-hCG and PAPP-A in the first trimester of pregnancy in a Chinese ethnic group. Implication for first trimester combined screening for Down's syndrome in the Chinese population.
OBJECTIVE
To study the effect of ethnic Chinese on the medians of free beta-hCG and PAPP-A in the first trimester of pregnancy.


METHODS
The data of 943 women undergoing first trimester combined screening for fetal Down syndrome were analysed to derive the Chinese-specific medians. The calculated risk of Down syndrome based on these Chinese-specific medians was compared with that based on the original algorithm of the Fetal Medicine Foundation (FMF).


RESULTS
The maternal serum levels of multiples of median of free beta-hCG and PAPP-A were significantly higher among the Chinese than among the Caucasians. The weight-adjusted gestation-specific medians were developed. Without adjustment for ethnicity, the original FMF algorithm underestimated the risk of Down syndrome by a median of 1%. Adjustment by ethnicity increased the false-positive rate by 10% (from 5.3 to 5.9%).


CONCLUSIONS
Ethnic Chinese have a significantly higher maternal serum level of free beta-hCG and PAPP-A in the first trimester, which could not be explained by differences in maternal weight. Adjustment for ethnicity may be necessary for these biochemical markers in a first trimester screening program.
Leung
Tak Yeung
TY
Department of Obstetrics and Gynaecology, Prince of Wales Hospital, Chinese University of Hong Kong, Hong Kong.
Spencer
Kevin
K
Leung
Tse Ngong
TN
Fung
Tak Yuen
TY
Lau
Tze Kin
TK
D015415:Biomarkers / Q000097:blood; D002681:China / Q000208:ethnology; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000175:diagnosis* / Q000208:ethnology*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000378:metabolism; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism*; D011296:Prenatal Diagnosis
D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A