A test to help physicians detect prostate cancer in patients has been approved by the federal Food and Drug Administration.

Routinely, men tested for the cancer are examined rectally and screened for high blood levels of prostate specific antigen, or PSA. The new "free PSA test" approved Wednesday is to be administered to patients when previous tests are inconclusive and doctors are unsure about the need to conduct a biopsy.FDA officials described the test as an "incremental advance."

While the free PSA test already is available in some clinics, the agency's approval allows the exam's manufacturer, Hybritech Inc. of San Diego, to market the product commercially.