Abstract for presentation at 11th International Congress of Human Genetics

Purpose: First trimester Combined Ultrasound and Biochemical (CUB) screening is offered to all women attending the Queen Mother’s Hospital in Glasgow. Only a small proportion of this screened population has a non-caucasian background and there is currently little information on the effect of ethnic origin on Free β human chorionic gonadotrophin (FβhCG) and pregnancy associated plasma protein A (PAPP-A) concentrations, Nuchal Translucency (NT) measurements or on screening performance.
Methods: We examined serum and ultrasound marker levels in 8382 caucasian women, 50 arabic women, 35 black women, 73 Chinese women, 128 Indian women, 195 Pakistani women and 14 South East Asian women with singleton pregnancies unaffected by a chromosome abnormality. All screening results were corrected for gestation and for maternal weight and smoking where appropriate. Compared to caucasian women, black women had significantly higher PAPP-A levels, with a median multiple of the median (MOM) of 1.60 (p<0.001). Chinese women had significantly higher FβhCG levels and NT measurements, with median MOMs of 1.12 (p<0.001) and 1.17 (p=0.01) respectively. Indian and Pakistani women had significantly reduced levels of FβhCG, with median MOMs of 0.85 (p<0.001) and 0.77 (p<0.001) respectively. No other statistically significant marker changes where found in any ethnic group. As a consequence of the increased PAPP-A concentration a reduced proportion of black women were assigned to the high risk group for Down’s syndrome when compared with caucasian women (2.9% versus 6.8%) while an increased proportion of Chinese women (17.8%) were assigned to the high risk group due to larger NT measurements and increased FβhCG concentration. Indian women had a lower false positive rate (1.6%) than Caucasian women but Pakistani women did not (6.2%).
Conclusions: In first trimester screening correction for ethnic origin will provide women with more accurate risks.