Distribution of prostate specific antigen (PSA) and percentage free PSA in a contemporary screening cohort with no evidence of prostate cancer

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Abstract
OBJECTIVE To explore the distribution of total prostate specific antigen (PSA) and percentage free/total PSA (%f/tPSA) in healthy volunteers with no clinical evidence of prostate cancer, who participated in prostate cancer screening. SUBJECTS AND METHODS PSA and %f/tPSA values from 2323 men, who participated in one of three annual prostate cancer screening events between 2004 and 2006, were tabulated according to age strata of 40–49, 50–59, 60–69 and 70–79 years. Local regression smoothing plots provided a graphical display of the relation between age and PSA or %f/tPSA, respectively. All PSA and %f/tPSA analyses were repeated for each age category after excluding, respectively, the top and the bottom 10% of PSA and %f/tPSA values. RESULTS Within the entire cohort, the median PSA level was 1.0 ng/mL and the median %f/tPSA was 25%. According to the age categories the PSA level and %f/tPSA medians within the entire cohort were, respectively, 0.7, 0.9, 1.3, 1.8 ng/mL and 28.0, 26.0, 24.0 and 25.0%. Of the 2323 men, 438 (18.9%) had a PSA level of >2.5 ng/mL and 1172 (50.5%) had a %f/tPSA of ≤ 25%. When either a PSA level of >2.5 ng/mL or a %f/tPSA of ≤ 25% were considered, 1235 (53.2%) had one or two abnormal values. Finally, if either a PSA level of >2.5 ng/mL or %f/tPSA of ≤ 15% was used, 617 (26.6%) were considered abnormal. CONCLUSION Half of men with no clinical evidence of prostate cancer should have PSA levels of 25%. A PSA level threshold of 2.5 ng/mL would require a biopsy in 20% of men and a %f/tPSA threshold of ≤ 25% in half of the men. Alternatively, a %f/tPSA threshold of ≤ 15% would decrease the probability to 15%.