Influence of first trimester biochemistry methodology on detection rate in screening for trisomy 21

The purpose of the study was to compare detection rates (DR) of FMF-certified and non-certified biochemical tests (BC) in trisomy 21 screening at 11-13 + 6 weeks.

In 2267 singleton pregnancies FMF-certified doctors measured crown to rump length (CRL) and nuchal translucency (NT). Serum samples were tested for free β-hCG and the PAPP-A using 2 analysers (Delfia - Perkin Elmer and Immulite 2000 - DPC), the results were expressed in MoM values and used for computer calculation of the risk for trisomy 21. The cut-off value for the high trisomy 21 risk was 1:300.

Comparison of free β-hCG MoMs by DPC and Delfia demonstrated statistically significant differences in normal, and trisomy 21 fetuses respectively. Similarly, statistically significant differences were noted for PAPP-A MoMs. The above differences in MoMs resulted in altered sensitivity in screening for aneuploidy. The application of the FMF-certified method ensures a markedly higher DR = 74%, compared to non-certified tests (64%), both at 5% FPR. The ROC analysis was performed in order to assess the efficacy of both tests. Results of trisomy 21 BC + NT risk scales using the Delfia and DPC methods are highly significant (p < 0.0001), which means that their discrimination ability is > 90%. The difference between results obtained using the Delfia and DPC methods is AUC = 0.0150 and is statistically significant (Z = 2.4728, p = 0.0134).

The use of FMF-certified first trimester biochemistry analysers improves DR for trisomy 21. The use of non-certified analysers causes reduction of DR and an increase of invasive procedure rate.