PSA (prostate-specific antigen), the blood test that is supposed to detect prostate cancer, correctly diagnoses the condition in just one out of four cases. This alarmingly high false-positive rate, revealed in a new study, throws into doubt the usefulness of the test, which is causing unnecessary distress among men who are mistakenly being told they may have prostate cancer.
The researchers who made the discovery are advising doctors to repeat the first positive test six weeks later before performing a biopsy. 'Even if the repeat test shows an elevated level, prostate cancer will only be discovered in about one quarter of men who undergo biopsy,' said Dr James Eastham of the research team.
In the study, which tracked blood tests on 972 men, blood levels returned to normal in over half the men who had tested positive in the first test.
Many things can raise PSA levels, including inflammation and recent ejaculation. So, even on the second reading, the test can still produce a positive result without there being a trace of prostate cancer. A better prostate test needs to be adopted, and quickly.
(Source: Journal of the American Medical Association, 2003; 289: 2695-700).