Comparison of combined, biochemical and nuchal translucency screening for Down syndrome in first trimester in Northern Finland.

Objective: To compare the efficacy of fetal nuchal translucency screening, maternal serum screening and combined screening for Down syndrome.

Methods: A prospective study. Methods: University hospital and its public health care district in Northern Finland. Methods: A total of 35,314 women participated in the first-trimester screening for Down syndrome within the public healthcare system in 2002-08. There were 95 pregnancies involving Down syndrome. Serum samples were obtained from 35,314 women, nuchal translucency was measured in 27,144 pregnancies and full combined screening was performed in those pregnancies, including 76 involving Down syndrome. Methods: The adjusted estimated risk for Down syndrome was calculated using the Perkin Elmer AutoDELFIA® time-resolved fluoroimmunoassay kit for the measurement of pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin. Nuchal translucency was measured by trained personnel in a university or district hospital. Risk cut-off figures 1:250 and 1:300 at term were used. Methods: Differences in detection rate, false-positive rate, positive and negative predictive values between nuchal translucency screening, serum screening and combined screening.

Results: Using the risk cut-off figure 1:250, the detection rates for serum screening, nuchal translucency screening and combined screening were 64.2, 64.5 and 72.4%, respectively and the false-positive rates were 7.8, 4.4 and 4.0%, respectively.

Conclusions: Combined screening is the method of choice for Down syndrome screening in Finland.