[Prostatic specific antigen (PSA). Interpretation of results as a function of the assay method]

The authors compare the two PSA assay methods most widely used in France. The first method (RIA Baxter) uses an isotope marker (Iodine 125), the other (EIA Biotrol) uses an enzymatic marker (alkaline phosphatase). PSA was assayed by means of these two techniques in 2 groups of patients: one group of 49 men considered to be free of any prostatic disease, recruited from blood donors; another group of 87 male patients in whom a PSA assay was performed prospectively at the first urology outpatients visit. The two PSA assay techniques gave different results, but the values obtained by these two methods were not discordant. It is therefore possible to define a coefficient of proportionality of 1.47 regardless of the PSA concentration or the urological disease considered (EIA Biotrol x 1.47 = RIA Baxter).