<strong>WATCH (above): A national task force says PSA testing fo prostate cancer can do more harm than good. Linda Aylesworth explains the new guidelines.</strong> VANCOUVER - New guidelines released by the Canadian Task Force on Preventive Health Care (CTFPHC) say the prostate-specific antigen (PSA) test is no longer effective as a prostate cancer-screening tool. <a href="http://www.cmaj.ca/lookup/doi/10.1503/cmaj.140703" target="_blank">These guidelines</a> say numerous cases of false positives and over-diagnosis could lead to potential harm. “While it might seem logical to diagnose cancers early and to provide treatment as quickly as possible, this might not be the case for prostate cancer detected through the PSA test, where possible benefits do not outweigh the potential harms of unnecessary biopsies and treatments," says Simon Fraser University health sciences professor Michel Joffres, who was part of the task force's guideline working group. The CTFPHC found that almost 20 per cent of men, ages 55 to 69, who had a PSA test received at least one false-positive, leading to about 18 per cent of the men undergoing unnecessary biopsies. A PSA test measures the blood level of prostate-specific antigens or PSAs, with the theory being the higher the levels of PSAs in a man's blood, the more likely it is that he has prostate cancer. “In the best case scenario, the PSA test might save one death from prostate cancer for every thousand people screened,” says Joffres in a release. “But it is crucial to note that other lives might be lost due to complications from biopsies and overtreatment as a result of screening. The PSA test therefore does not have an effect on overall mortality.” The updated guidelines now recommend against using the PSA test to screen for prostate cancer in men younger than 55 years old and older than 70 years old. They also recommend not using the PSA test for men ages 55 to 69, but say "men who place a high value on a small potential reduction mortality and are less concerned with undesirable consequences may choose to be screened."