Examination of a first-trimester Down syndrome screening concept on a mix of 11,107 high- and low-risk patients at a private center for prenatal medicine in Germany.

OBJECTIVE

To assess the performance of a combined first-trimester screening concept for trisomies 21, 18 and 13 applied to a low- and high-risk patient sample in a specialized private center for prenatal medicine.

STUDY

DESIGN

The quality of different first-trimester screening algorithms (risk calculation based on maternal age and nuchal translucency alone, maternal age and serum parameters (free beta-hCG and PAPP-A) alone and a combination of both) was evaluated in a study population of low- and high-risk cases for fetal aneuploidies. All measurements were performed between the 11th+0 and 13th+6 weeks of gestation during the study period from November 2000 to December 2006, in accordance with the guidelines of the Fetal Medicine Foundation (FMF), London.

RESULTS

Of 11,107 women included in the study, we had a complete follow-up on 10,668. The difference between the detection rate was insignificant for both the low-risk and the high-risk groups. In the overall study population, 52 of 59 cases of trisomy 21 were detected when a pre-defined cut-off of 1:300 was applied (detection rate (DR) 88.1%; 95% confidence interval (CI): 79.8-96.4 and false-positive rate (FPR) 4.9%; 95% CI: 4.5-5.3). For trisomies 13 and 18 with a pre-defined cut-off of 1:150, 26 of 32 cases were detected (DR 81.3%; 95% CI: 67.8-94.8 and FPR 0.7%; 95% CI: 0.5-0.9). The highest sensitivity was between 11+0 and 11+6 weeks of gestation with all cases of trisomy 21 detected with a FPR 5.1%; 95% CI: 3.7-6.5.

CONCLUSION

In our study population of different risk categories, the detection rate using the combined risk calculation based on maternal age, fetal NT, maternal PAPP-A and free beta-hCG levels was superior to the application of either parameter alone.