THE PERCENTAGE OF FREE PROSTATE-SPECIFIC ANTIGEN IS AN AGE-INDEPENDENT TUMOR-MARKER FOR PROSTATE-CANCER - ESTABLISHMENT OF REFERENCE RANGESIN A LARGE POPULATION OF HEALTHY-MEN

Objective To define the reference range for the ratio of free to total prostate-specific antigen (fPSA%) in a population of healthy men with no clinically evident prostate cancer and to assess the influence of age on this tumour marker, thus determining the utility of fPSA% in en hancing the discriminatory power of PSA to differentiate healthy men a nd patients with benign prostatic hyperplasia from those with prostate cancer. Subjects and methods In a prospective cohort study between Ma y and August 1996, 1160 white men aged 20-89 years (957 were 40-69 yea rs old, 82% of all subjects) from nine European and eight non-European countries were assessed. None of the participants who had a history o f prostate cancer had undergone prostatectomy. A standard clinical exa mination including a digital rectal examination was performed to exclu de the presence of prostate cancer. Transrectal ultrasonography was no t an inclusion criterion, as it was not available in every case, Total PSA (tPSA) and free PSA (fPSA) were determined in 61 laboratories usi ng the appropriate Enzymun-Test(R) for tPSA and fPSA (Boehringer Mannh eim Diagnostics, Mannheim, Germany). Serum tPSA, fPSA and fPSA% were t hen assessed as a function of the subjects' age, Results The serum tPS A and fPSA were significantly different among age decades 2-8 (P<0.001 ), with increasing median values, indicating that both variables depen d on age. The recommended upper reference limit (95th percentile) for tPSA is 1.78 ng/mL for men aged 30-39 years, 1.75 ng/mL for 40-49 year s, 2.27 ng/mL for 50-59 years, 3.48 ng/mL for 60-69 years and 4.26 ng/ mL for 70-79 years. The fPSA% was not significantly different between decades 3-8 (P=0.06), Those aged 20-29 years had a slightly higher med ian value (P=0.03) than the other age groups. The recommended lower re ference limit (fifth percentile) for fPSA% is 12.6%. Conclusion The fP SA% for clinically relevant age groups in healthy men was independent of age, which simplifies the use and interpretation of this relatively new tumour marker.