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PSA (free and protein bound)

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The most common PSA test measures the total amount of PSA (both free and protein bound) in the blood:

  • an alternative test has been used which calculates the ratio of free: total PSA. Free PSA is associated with benign conditions while bound PSA is associated with malignancy. Hence a low ratio (<25%) may be indicative of cancer (1,2)
  • evidence suggest that reflex testing with PSA isoforms, such as ratio of free to total PSA (f/tPSA) or complex PSA (cPSA), for men with PSA values <10 ng/mL (known as the diagnostic “grey zone”) could improve specificity and reduce the number of unnecessary biopsies
    • triage of men in the “grey zone” with tPSA 2 to 10 ng/ml using PSA isoforms could potentially reduce overdiagnosis and maintain a high cancer detection rate

Free/total PSA is of no clinical use if total serum PSA is > 10 ng/mL or during follow up of known PCa (3)

Reference:


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