Survey of Prostate Specific Antigen Tests (PDF 101Kb)
Second Survey of Prostate Specific Antigen Tests (PDF 121 Kb)
Prostate Specific Antigen (PSA) exists in different forms (isoforms). It can be joined to other proteins when it is often referred to as complexed PSA, or it can exist on its own, known as free PSA.
The PSA tests commonly referred to and used in Prostate Cancer Risk Management are total PSA tests. This means that they detect both free and complexed PSA to give a measure of all PSA present in the blood sample.
Total PSA tests used in Prostate Cancer Risk Management to measure PSA levels in men with no symptoms of prostate disease, have to meet certain quality criteria. There is ongoing work with the NHS Centre for Evidence-based Purchasing to regularly evaluate PSA tests against these criteria.
A report of the most recent findings is available, Evaluation Report - Total PSA Assays (PDF 76Kb).
PSA tests that measure only free or complexed PSA do exist. The relative proportions of free and complexed PSA are thought to be different in men with prostate cancer when compared to men with other prostatic diseases where the total PSA level is also raised. Men with cancer are thought to have a smaller proportion of free PSA and more complexed PSA than men with other benign prostatic diseases such as benign prostatic hyperplasia (BPH) or prostatitis.
Free or complexed PSA tests are provided by some laboratories. They are often used as follow on tests following a raised total PSA test result. The results are reported as the percentage of free PSA compared with the total amount of PSA detected. Any results below a cut-off value are thought to be suggestive of prostate cancer. These free or complexed PSA tests are designed to be used when the total PSA test result is marginally raised, and not in cases where the total PSA test result is very high and suggestive of advanced prostate cancer.
Urological referral of asymptomatic men in general practice in England
A peer review paper has been published in the British Journal of Urology International1.