RESUMO
PURPOSE: To analyze intraindividual variations of total and percent free serum prostate-specific antigen (PSA) in patients with normal digital rectal examination. MATERIAL AND METHODS: Total and free serum PSA were determined in two blood samples corresponding to 107 nonconsecutive patients. The period between both determinations ranged from 23 to 60 days. Prostatic biopsy was done after both determinations in all except 17 patients because the two serum PSA concentrations were <4 ng/ml. Total and free PSA were determined using double monoclonal antibody immunoassay Tandem and Tandem free (Hybritech Inc.). The diagnosis was benign prostatic hyperplasia (BPH) in 63 patients and prostate cancer (PCA) in 44. RESULTS: The variations of PSA ranged between -6.8 and +3.2 ng/ml in BPH patients and between -2.8 and +9.0 in patients with PCA. The median coefficients of variation were 15.4 and 15.7% respectively. The variations in the percent free PSA were between -30.7 and +40.9 in the BPH group and between -17.9 and +15.8 in the PCA group. The median coefficients of variation were 32.2 and 32.3% respectively. If prostatic biopsy had been indicated when percent free PSA had been
