Variation of Serum Prostate-Specific Antigen Levels

ContextSerum prostate-specific antigen (PSA) testing is frequently used in early detection programs for prostate cancer. While PSA testing has resulted in an increase in prostate cancer detection, its routine use has been questioned because of a lack of specificity.ObjectiveTo determine whether year-to-year fluctuations in PSA levels are due to natural variation and render a single PSA test result unreliable.Design, Setting, and ParticipantsRetrospective analysis of an unscreened population of 972 men (median age, 62 years) participating in the Polyp Prevention Trial (1991-1998). Five consecutive blood samples were obtained during a 4-year period and were assessed for total and free PSA levels.Main Outcome MeasureAbnormal PSA test result based on a PSA level higher than 4 ng/mL; a PSA level higher than 2.5 ng/mL; a PSA level above the age-specific cutoff; a PSA level in the range of 4 to 10 ng/mL and a free-to-total ratio of less than 0.25 ng/mL; or a PSA velocity higher than 0.75 ng/mL per year.ResultsProstate biopsy would have been recommended in 207 participants (21%) with a PSA level higher than 4 ng/mL; in 358 (37%) with a level higher than 2.5 ng/mL; in 172 (18%) with a level above the age-specific cutoff; in 190 (20%) with a level between 4 and 10 ng/mL and a free-to-total ratio of less than 0.25 ng/mL; and in 145 (15%) with a velocity higher than 0.75 ng/mL per year. Among men with an abnormal PSA finding, a high proportion had a normal PSA finding at 1 or more subsequent visits during 4-year follow-up: 68 (44%) of 154 participants with a PSA level higher than 4 ng/mL; 116 (40%) of 291 had a level higher than 2.5 ng/mL; 64 (55%) of 117 had an elevated level above the age-specific cutoff; and 76 (53%) of 143 had a level between 4 and 10 ng/mL and a free-to-total ratio of less than 0.25 ng/mL.ConclusionAn isolated elevation in PSA level should be confirmed several weeks later before proceeding with further testing, including prostate biopsy.