EVALUATION OF THE COBAS CORE IMMUNOASSAY FOR MEASURING PROSTATE-SPECIFIC ANTIGEN (PSA) - MULTICENTER STUDY RESULTS

Hoffmann-La Roche has introduced a fully automated COBAS CORE EIA for the measurement of prostate specific antigen (PSA). A regular and an u ltrasensitive version of the assay are available. Both versions of the COBAS CORE PSA EIA were compared with the established IMx PSA assay f rom Abbott. Sera from 98 apparently healthy males, 224 patients with b enign prostate hyperplasia, 17 patients with prostatitis and 111 patie nts with prostate cancer were determined using the COBAS CORE PSA EIA in comparison with the IMx PSA assay. The sera were drawn before treat ment. Sera from 26 patients were also monitored through follow-up test ing. The COBAS CORE analyser allows rapid analysis of large series of samples. Intra-assay imprecision (CV) was between 1.7% and 4.9% (IMx P SA: between 2.4% and 2.7%). The coefficient of variation for inter-ass ay imprecision was between 3.4% and 6.5% (IMx PSA: between 3.2% and 3. 3%). The analytical detection limit was determined as 0.2 mu g/l for t he regular COBAS CORE PSA EIA and 0.05 mu g/l for the ultrasensitive v ersion. A biological detection limit of 0.1 mu g/l was determined for the ultrasensitive version. Results obtained using the COBAS CORE PSA EIA and IMx PSA assays were in excellent correlation: coefficient of c orrelation r = 0.99 and slope = 0.92, using prostate-specific antigen values from the complete study. Only in the measuring range below 10 m u g/l did the coefficients of correlation vary between 0.82 and 0.93. The diagnostic sensitivity for both assays is approximately the same: at a specificity of 95% with regard to benign prostate hyperplasia, th e COBAS CORE PSA EIA showed a sensitivity of 41% and the IMx PSA assay a sensitivity of 47%. In the follow-ups of all 26 patients, the two a ssays showed very good correspondence. The regular COBAS CORE PSA EIA performs similarly to the IMx PSA assay with respect to reproducibilit y and diagnostic sensitivity. Values from both assays compare well wit h each other. The biological detection limit for the ultrasensitive ve rsion of the COBAS CORE PSA EIA differs only slightly from that for th e IMx PSA assay.