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.