Serum alpha-fetoprotein: II. Clinical evaluation of two automated immunoassays for maternal serum screening

A prospective clinical evaluation is reported for analysis of maternal serum alpha fetoprotein (s.AFP) testing by recently developed enzymeimmunoassay automated systems. The reference method for the study was a manual competitive binding radioimmunoassay which has been utilized by us in the Maternal Serum AFP Screening Program at the Medical University of South Carolina for the past five years. The patients were classified by weeks of gestation, 16 to 20. Mean concentrations of s.AFP increased with the increase in gestational week for each method; calculated multiples of median (MoM) values remained relatively constant regardless of the week of gestation. Mean and median concentrations of s.AFP measured by the radioimmunoassay and the coated tube enzymeimmunoassay methods showed close agreement, indicating the direct transferability of the methods for clinical purposes. The microparticle capture enzymeimmunoassay yielded higher results of s.AFP indicating the necessity for a correction if the method transfer is to be considered for sequential patient testing. (Multiples of median values for each method were uncorrected for maternal age, weight, or diabetes mellitus; lack of correction would not affect comparison of methods for clinical application.