Guidelines for doctors from a national task force on PSA testing say the practice shouldn’t be used to screen men for possible prostate cancer – because it can lead to more harm than good.

The Canadian Task Force On Preventive Health Care says that measuring “prostate specific antigen,” or PSA in blood isn’t an effective screening tool – because it often produces false-positive results – which lead to unnecessary treatment.

Task force member Doctor Neil Bell says almost one-in-five men aged 55 to 69 encounter at least one false-positive PSA test – and approximately 17 percent end up with unnecessary biopsies.

Bell says more than half of detected prostate cancers are over-diagnosed – meaning they wouldn’t have caused symptoms or death during a man’s lifetime.

Over-diagnosis often leads to treatments that can cause impotence, incontinence and infection – but Bell says PSA screening results in only a 0.1 percent reduction in prostate cancer deaths – or one less death – per one thousand men.

The Task Force recommendation applies only to using PSA tests to discover if a patient might have prostate cancer – not for checking whether treatment is working in men who have already been diagnosed with the disease.