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 == Prostate specific antigen ==
-Prostate specific antigen (PSA) is a protein produced in the prostate. It is elevated in [[prostate cancer]] but also [[prostatitis]] and [[benign prostatic hyperplasia]]. It should not be measured after [[digital rectal examination]], as this artificially elevates the PSA.
+Prostate-specific antigen (PSA) is an enzyme that is produced only by the prostatic glandular epithelium, which is why its level correlates to the number of prostatic glands in the body. Its level is elevated in [[prostate cancer]] but can also be increased in [[prostatitis]] or [[benign prostatic hyperplasia]], so it’s not specific for cancer. PSA is considered elevated above 4 ng/mL. It should not be measured after [[digital rectal examination]], as this artificially elevates the PSA.
-PSA in plasma is mostly bound to a carrier protein, while a small fraction is free. The fraction that is free is lower in malignancy than in benign causes of elevated PSA and can be used to help differentiate them.
+In addition to measuring the total level of PSA, one can also measure other parametres such as free PSA, PSA density, PSA velocity, complexed PSA, and percentage of [-2]proPSA (a precursor of PSA). PSA in plasma is mostly bound to a carrier protein, while a small fraction is free. While decreased free PSA is known to be more specific for prostate cancer than total PSA, the clinical utility of the other parametres is not yet established and so they're not much used.
-PSA is sometimes used for screening for prostate cancer, but this is controversial. Screening decreases mortality from prostate cancer but also causes overtreatment, as many of those who will receive cancer therapy (with all the complications and side effects it causes) due to detection of prostate cancer on screening would never have developed a clinically significant cancer.
+PSA is sometimes used for screening for prostate cancer, but this is controversial. Screening decreases mortality from prostate cancer but also causes overtreatment, as many of those who will receive cancer therapy (with all the complications and side effects it causes) due to detection of prostate cancer on screening would never have developed a clinically significant cancer. Elevated PSA might not necessarily correlate to a clinically active cancer, so its usefulness should be determined on a case-by-case basis. PSA does have great value in measuring the effectiveness of therapy though.
 == Alpha-foetoprotein ==