BETHESDA, Md--Physicians who screen for prostate cancer using prostate-specific antigen (PSA) need to use a different set of normal age-adjusted values for their African-American patients, say Judd W. Moul, MD, LTC, MC, USA, and colleagues from the Walter Reed Army Medical Center, Mayo Clinic, and Uniformed Services University of the Health Sciences funded by the Department of Defense (DOD) Center for Prostate Disease Research.
The reference ranges in common use were derived from white populations, Dr. Moul says. His study compared PSA levels in 3,475 men (all military personnel) with no clinical evidence of prostate cancer (1,802 white and 1,673 black) and a group of 1,783 men with prostate cancer (1,372 white and 411 black).
The investigators found that PSA levels were significantly higher in black men (mean, 1.48 ng/mL in controls and 7.46 ng/mL in patients) than in whites (1.33 ng/mL in controls, 6.28 ng/mL in patients). In addition, there was more variation in PSA levels with increasing age among blacks than among whites.
Traditional age-specific reference ranges continued to work well when applied to the data on whites, but would have missed 41% of cases of prostate cancer in blacks, with the test specificity kept at 95%. "This poor sensitivity is especially disturbing because black men are at higher risk than white men," Dr. Moul writes in the New England Journal of Medicine (335:304-310, 1996).
The problem was the traditional strategy's 95% specificity, which resulted in very low sensitivity for blacks. The researchers then used their new PSA data to develop reference ranges that would have 95% sensitivity and acceptable specificity for blacks (see table,).
AUA Endorses New Ranges
The American Urological Association (AUA) hailed the new research as "unusually significant" because it will alert physicians to the special need for early detection of prostate cancer and help urologists better diagnose prostate cancers earlier in African-American men.