Studies Find PSA Screening Unreliable

Sept. 26 -- FRIDAY, Sept. 25 (HealthDay News) -- The inability of the prostate specific antigen (PSA) test to distinguish between deadly and harmless prostate cancers makes it unusable as a population-wide screening tool, new research claims.

Because of its unreliability, results from the test lead to overdiagnosis and overtreatment, according to two reports in the Sept. 25 online edition of BMJ.

"Our findings strongly indicate that, in addition to PSA, further biomarkers are needed before inferring population-based screening for prostate cancer," said Benny Holmstrom, a urologist with Gavle Hospital in Gavle, Sweden, and lead author of the first study.

Holmstrom's group studied the PSA tests of 540 men diagnosed with prostate cancer. Their PSA was measured several years before being diagnosed. They compared those tests with PSA tests from 1,034 men without prostate cancer.

"Our main finding was that no cut-off level for PSA attained the criteria formally required for a screening test," Holmstrom said. "Furthermore, we found that in men with a prediagnostic PSA level below 1 nanogram per milliliter, only six men [1.2 percent] were later diagnosed with a high-risk prostate cancer. Hence, PSA levels below [that] almost ruled out a future high-risk prostate cancer diagnosis."

"The direct implication of our findings in a screening situation is that no matter which PSA cut-off you adopt for selecting men for further diagnostic work-up, you will either have too many false positives or too many false negatives," said study co-author Mattias Johansson, a postdoctoral fellow at Umea University in Sweden.

"Given the current trend in lowering the PSA cut-off to about 3 nanograms per milliliter, it seems clear that a large number of healthy men will be subject to painful, stressful and costly diagnostic procedures," he said. "In addition, and perhaps more serious, is the wide overdiagnosis of slow-growing tumors causing unnecessary medical treatment and anxiety."