Intraindividual variations of total and percent free serum prostatic-specific antigen levels in patients with normal digital rectal examination

Purpose: To analyze intraindividual variations of total and percent free se rum 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 per iod between both determinations ranged from 23 to 60 days. Prostatic biopsy was done after both determinations in all except 17 patients because the t wo serum PSA concentrations were < 4 ng/ml. Total and free PSA were determi ned using double monoclonal antibody immunoassay Tandem and Tandem free (Hy britech Inc.). The diagnosis was benign prostatic hyperplasia (BPH) in 63 p atients and prostate cancer (PCA) in 44. Results:The variations of PSA rang ed 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 a nd +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 pros tatic biopsy had been indicated when percent free PSA had been less than or equal to 25 in the PSA range of 4.1-10 ng/ml, we would have found discrepa ncies in 15% of all the patients. The sensitivity for the first determinati on would have been 100 and 94.4% for the second. The rate of negative biops ies would have been reduced by 16.6 and 19.4% respectively. Conclusions: In traindividual variations in serum PSA concentration and percent free PSA co uld have clinical implications in the decision to perform prostatic biopsy.