Urine free beta-hCG and total estriol for Down syndrome screening during the second trimester in an Asian population

Objective: To evaluate second-trimester free β-hCG and total estriol (E3) in the maternal urine as markers for Down syndrome screening in an Asian population. Methods: Free β-hCG and total E3 were measured in the urine samples of 28 Taiwanese Down syndrome pregnancies and 268 unaffected singleton pregnancies at 14-25 weeks. Results were normalized to urine creatinine concentrations and converted to multiples of the median (MoM) levels. Gestational ages were estimated by ultrasound measurements. Results: Median values of free β-hCG, total E3, free β-hCG to total E3 ratio, and the free β-hCG to total E3 MoM ratio in Down syndrome pregnancies were 4.75 MoM, 0.66 MoM, 8.99 MoM, and 9.51, respectively. At a 5% false-positive rate, the observed detection rates were 36% (ten of 28) with total E3, 71% (20 of 28) with free β-hCG, 68% (19 of 28) with free β-hCG/total E3, and 71% (20 of 28) with free β-hCG/total E3 MoM. When combined with maternal age, the expected detection rates were 65% with total E3, 71% with free β-hCG, 76% with free β-hCG/total E3, 80% with free β-hCG/total E3 MoM, and 89% when combining free β-hCG, total E3, and maternal age. Conclusion: Urine free β- hCG and total E3 are useful markers for Down syndrome screening during the second trimester in Taiwanese women.