Total, free, and percent free prostate-specific antigen levels among U.S. men, 2001-04.

Abstract

Objective: Screening for prostate cancer using prostate-specific antigen (PSA) tests is common but remains controversial. Total PSA using thresholds of 4.0 and 2.5 ng/mL has been used for screening men. In addition, the percent free PSA (free PSA/total PSA x 100%) using thresholds of less than 25% and 15% have been proposed for use in screening for prostate cancer in conjunction with the total PSA. The distributions of total PSA, free PSA, and percent free PSA, which vary with age and race-ethnicity among American men, would help determine the burden of screening using different thresholds of PSA tests.

Methods: PSA tests were performed on serum samples from men age 40 years and older (n = 2,546) who participated in the 2001-04 National Health and Nutrition Examination Survey (NHANES). Total, free and percent free PSA were estimated for Mexican American, non-Hispanic white, and non-Hispanic black men.

Results: About 6.2%, (95% confidence interval, 95% CI: 5.2-7.2%), corresponding to an estimated 3.6 million (95% CI: 3.0-4.2 million) men 40 years of age and older, had a total PSA of greater than or equal to 4.0 ng/mL. Approximately 3.6% (95% CI: 1.8-6.2%) of Mexican American men, 6.2% (95% CI: 5.1-7.6%) of non-Hispanic white men, and 7.8% (95% CI: 5.2-11.1 ) of non-Hispanic black men had total PSA of 4.0 ng/mL or more. Approximately 13.1 (95% CI: 11.7-14.5%) of men 40 years of age and older had total PSA greater than or equal to 2.5 ng/mL. For men with total PSA less than 2.5 ng/mL, 23.1% (95% CI: 21.0-25.3%) had a percent free PSA between 15% and 25%, and 5.0% had free PSA (95% CI: 3.9-6.4%) less than or equal to 15%.

Conclusions: The effect of lowering the total PSA thresholds increases the number of U.S. men who would be referred for screening for prostate cancer. Total and free PSA increased with age in Mexican American, non-Hispanic white, and non-Hispanic black men. Information about the distribution of total, free, and percent free PSA will help guide public health policy in screening for prostate cancer.