Prostate-specific antigen as a marker for prostatic cancer: a monoclonal and a polyclonal immunoassay compared

We evaluated the clinical utility of prostate-specific antigen (PSA) in diagnosis and management of prostatic cancer, using a monoclonal immunoradiometric assay (M-PSA) and a polyclonal radioimmunoassay (P-PSA). Assay CVs ranged from 1.3% to 4.9% (M-PSA) and from 5.1% to 8.0% (P-PSA). Detection limits were 0.1 microgram/L (M-PSA) and 0.2 microgram/L (P-PSA). Reference intervals established for healthy men were: 0-2.8 micrograms/L (M-PSA) and 0-4.2 micrograms/L (P-PSA). The regression equation for the PSA concentrations (0-100 micrograms/L) measured in normal men, men with primary prostatic cancer, and men with benign prostatic hypertrophy (BPH) was: P-PSA = 1.603 M-PSA - 0.120 microgram/L (r = 0.9923, n = 201). The P-PSA calibrators yielded one-half their assigned values when analyzed by the M-PSA assay. With either assay there were proportional increases in PSA values with advancing cancer. The proportion of PSA values exceeding the reference interval was 50% for patients with stage A prostatic cancer, 80% (stage B), 100% (stages C and D), and 65% for men with BPH. After radical prostatectomy, the follow-up PSA values for most patients were within the reference intervals for women (0-0.2 microgram/L for M-PSA, 0-0.8 microgram/L for P-PSA). Most patients with above-normal PSA values have clinically detectable disease.