A technical and clinical evaluation of a new assay for inhibin A and its use in second trimester Down syndrome screening

Background: The objective of the study was to compare a new AutoDELFIA(R) Inhibin A kit (B064-102) with the Access Inhibin A kit (A36097) using clinical specimens and to evaluate the AutoDELFIA(R) Inhibin A assay performance in screening for Down syndrome in the second trimester of pregnancy. Methods: Using clinical samples, we performed a method comparison between new and existing inhibin A kits and assessed AutoDELFIA(R) Inhibin A kit precision performance. Normal median values for the second trimester of pregnancy were also determined. Finally, we evaluated the screening performance of the AutoDELFIA(R) Inhibin A kit together with other second trimester biomarkers for the detection of Down syndrome. Results: The two methods showed a high degree of correlation (r = 0.99, Pearson and Spearman correlation), and the average relative level difference between the methods at a concentration range of 41.7-1925 pg/mL was 19.6% [95% confidence interval (CI) from 17.6% to 21.5%]. The acceptable precision of the AutoDELFIA(R) Inhibin A kit was demonstrated: the within-lot CV% varied from 1.9% to 3.9%. The screening performance results show that AutoDELFIA(R) Inhibin A when added to a combination of other second trimester serum markers [human alpha foeto-protein (hAFP), free beta subunit of human chorionic gonadotropin (free hCG beta) and unconjugated estriol (uE3) or hAFP and free hCG beta] improves the detection rate of screening in both combinations. Conclusions: The performance of the AutoDELFIA(R) Inhibin A assay is highly acceptable for routine laboratory use for screening Down syndrome in the second trimester of pregnancy.