Men who are healthy should not be given a blood test to screen for prostate cancer, the government is set to report next week.

The test was found to be unreliable in predicting whether a man will actually become ill from prostate cancer, and was more likely to lead to unnecessary tests and treatment, according to five studies of men in the U.S. and Europe.

The PSA test, as it is known, is now widely used by doctors treating men 50 and older. Often the test is done without the patient’s knowledge, with a blood sample taken during an annual physical, for instance. Of the 44 million American men age 50 and older, 33 million of them have had the PSA test.

The government task force that issued the recommendation, called the United States Preventative Services Task Force, is the same one that recently dialed back on years of medical advice and announced that women under 50 should no longer have mammograms.

In both instances, the members of the task force found the tests did more harm than good, with many patients treated for cancers that were slow growing and unlikely to affect their health.

In the case of prostate cancer, it was found that a positive result from the PSA test led patients down a long road of tests and treatment that often resulted in impotence and incontinence, without improving outcomes.

The task force also found that men with fast-growing prostate cancers were not helped by the PSA test, as there is no evidence that earlier treatment was more effective.

The PSA test has long been known as unreliable, having a high rate of false positives and false negatives. But many leading physicians have insisted it’s better than no test at all.

Dr. Eric Klein of the Cleveland Clinic told the New York Times that he thought there was “a substantial amount of evidence from randomized clinical trials that show that among younger men, under 65, screening saves lives.”

Medicare will continue to pay for annual P.S.A. testing for men 50 and older, as it is required to do so by federal law.