Comparison of four different analyzers for prenatal trisomy 21 risk

Various analyzers are available for measuring first-trimester combined screening for trisomy 21 (T21) serum biomarkers (free-beta subunit of the human chorionic gonadotropin (β-hCG) and the pregnancy-associated plasma protein A (PAPP-A)). Our aim is to compare the analytical performance of four different analyzers and their false positive rates (FPR) for T21 risk.

A 6-month study analyzed data from 1,136 pregnant women for first-trimester combined screening. Serum samples were processed using four analyzers (IMMULITE 2000, Centaur XP, Cobas e-411, KRYPTOR compact PLUS), each with its own risk calculation software. Comparative analyses of the biochemical markers and their multiples of the median (MoMs) were conducted using Passing-Bablok and Bland-Altman methods.

Significant variability was observed among the analyzers. For free β-hCG, only Centaur XP and KRYPTOR compact PLUS were interchangeable. For PAPP-A, only IMMULITE 2000 and Cobas e-411 were comparable. However, no analyzer pair was interchangeable for both markers simultaneously. Free β-hCG multiples of the median (MoMs) were highest in IMMULITE 2000 (1.85 MoM (IQR: 1.4-2.97)) and lowest in KRYPTOR compact PLUS (1.5 MoM (IQR: 1.23-2.21)). PAPP-A MoMs were lowest in IMMULITE 2000 (0.52 MoM (IQR: 0.38-0.82)) and highest in Cobas e-411 (0.58 MoM (IQR: 0.39-0.90)). In risk assessment, all analyzers detected true T21 cases but varied in their FPR, with Centaur XP (3.8 %), Cobas e-411 (2.5 %) and KRYPTOR compact PLUS (2.3 %) showing a FPR below 5 %.

Measurement of serum biomarkers by the four analyzers is not interchangeable. KRYPTOR compact PLUS showed the lowest FPR for risk assessment.