One of the problems with screening tests for cancer is that there is an assumption that if you have a negative test, you don't have cancer. Many people just don't realise that you can have cancer with a negative screening test. For prostate cancer serum PSA levels of 4 μg/L or more are considered to show the possible presence of cancer. An analysis of men in a large randomised study shows that cancer is also found in men with lower levels.

Although the risk of finding a cancer on biopsy is directly related to PSA levels below 4 μg/L, there is no PSA value below which a man has no risk of prostate cancer. Moreover, this statement applies not just to any grade of prostate cancer, but even to high grade cancers where disease progression in the absence of treatment is to be expected.

Its importance is that it is a harsh reminder of the failures as opposed to the benefits of screening. Older men with normal PSA values of 4 μg/L or below should still be on the lookout for warning signs, as 1 in 8 will have prostate cancer worth treating despite that normal result.
About the Author

A Certified Family Physician of the Philippine Academy of Family Physician and continue to complete the requirements for Continuing Medical Education in Family Practice. Also a member of the Philippine Medical Informatics Society, Philippine Occupational Health and Safety Inc., and Pangasinan Medical Society. Faculty Department of Physiology (Medicine) Lyseum- Northwestern University, Dagupan, Pangasinan, Faculty Medical Informatics Lyseu