ABSTRACT
Prostate-specific antigen (PSA), also known as gamma- seminoprotein or kallikrein-3 (KLK3), is a glycoprotein enzyme encoded in humans by the KI.K3 gene. PSA is a member of the kallikrein-related peplidase family and is secreted by the epithelial cells of the prostate gland. Prostate cancer has come to share the oncological centrestage among male cancers. The availability of Serum Prostate Specific Antigen, PSA, as a marker has encouraged it is use lo diagnose both cancer and cancer recurrence. Some clarity is required about its precise role in clinical practice. The available literature on Prostate Specific Antigen was reviewed; Articles were reviewed for content, applicability to the problem at hand, availability of data about sensitivity and specificity of values, refinements in measurements and finally for impact of screening programmes using these values on survival and quality of life. The data in the literature was critically re-evaluated and analysed to draw reasonable conclusions. Serum PSA measurements show variable reliability when it comes to diagnosis of Prostate cancer, given the dynamics of PSA physiology. Surrogate measures like PSA density, PSA velocity, free-to-complexed PSA ratio, percentage Pro-PSA, etc.. have been used to improve the predictive utility of this assay for Prostate cancer The ability of PSA to detect those cancers that will cost life, and thereby permit early curative treatment, is as yet unclear. It's most definitive role appears to be in diagnosing recurrences after adequate surgical treatment, and in evaluating response to treatment. Only 30 percent of patients with high PSA have prostate cancer diagnosed after biopsy. PSA is normally present in the blood at very low levels- Increased levels of PSA may suggest the presence of prostate cancer. However, prostate cancer can also be present in the complete absence of an elevated PSA level, in which case the test result would be a false negative. PSA levels can be also increased by prostatitis, irritation, benign prostatic hynerplasia (13PH), and recent ejaculation, producing a false positive result. The normal reference ranges for prostate-specific antigen increase with, as do the usual ranges in cancer.
