Free PSA (fPSA)
Sample: Serum
Schedule: Daily
Units: % of total PSA
Range: > 20% Acceptable 10 - 20 % Indeterminate < 10% Decreased
Remarks: Serum PSA (Prostatic Specidfic Antigen) levels increase due to changes in the prostate gland caused by trauma, infection, inflammation, prostate manipulation, benign prostatic hypertrophy or malignancy. In serum, total PSA consists of free (fPSA)and bound PSA, whereas most PSA is bound to inhibitor proteins. Patients with total PSA between 4 and 10 ng/mL and fPSA less than 20% of the total, have increased risk of prostate cancer.
On the other hand, some autors claim that complex PSA (cPSA) is better discriminator than fPSA/PSA ratio. cPSA is a group of at least three differents molecules of PSA (different from fPSA). Nevertheless, latest studies indicate that, at least up to date, it is unclear if cPSA offers better discrimination for more accurate diagnosis of prostate disseases. At present, cPSA is only a little better than total PSA (tPSA) when is used as first screening test for postate disease.
