Comparison of measured concentration values of biochemical serum markers with two immunoassay systems in first trimester screening for fetal aneuploidy.

Non-invasive first trimester screening for fetal aneuploidy is based on the consideration of fetal nuchal translucency, biochemical serum markers 'pregnancy associated plasma protein A' (PAPP-A), and 'free beta-humane chorionic gonadotropin' (fβ-hCG). The blood sera of 168 pregnant women in 11 + 0 to 13 + 6 weeks of gestation were examined by both the COBAS (Roche Holding GmbH, Germany) and KRYPTOR (Brahms GmbH, Germany) immunoassay systems in two quality controlled laboratories. The concentration values were converted into multiple of median (MoM) values and compared through a two-tailed t test. The concentration values of PAPP-A differed significantly from each other (p < 0.0001). COBAS produced on average 0.09 MoM higher values in comparison to KRYPTOR (CI 95% = 0.06-0.11 MoM). In contrast, the concentration values of fβ-hCG did not differ significantly (p value = 0.20). The values produced by COBAS were on average only 0.02 MoM higher in comparison to KRYPTOR (CI 95% = -0.01 to 0.05 MoM). Which of the two systems generates the more precise results should be evaluated in a large-scale prospective study with the pregnancy outcomes.