The ease of calibration and the accuracy of free PSA assays in comparison with assays of the PSA-ACT complex suggest that measurements of free to total PSA most accurately reflect the inverse of the proportion of PSA complexed to ACT in serum.
Complexed PSA: This test directly measures the amount of PSA that is attached to other proteins (the portion of PSA that is not "free"). This test could be done instead of checking the total and free PSA, and it could give the same amount of information, but it is not widely used.Circulating PSA can be divided into two main forms: complexed and free. Most circulating PSA is bound to a variety of protease inhi- bitors, most commonly a-1-antichymotrypsin, and the proportion of the total PSA concentration which is free or unbound is relatively small.PSA, a protein produced by prostate gland cells, circulates through the body in two ways: either bound to other proteins or on its own. PSA traveling alone is called free PSA. The free-PSA test measures the percentage of unbound PSA; the PSA test measures the total of both free and bound PSA.
We selected serums from 51 fully characterized prostate cancer patients and 48 biopsy-proven BPH patients in order to test the ability of the ratio of the free/total PSA in distinguishing between CaP and BPH patients in the best case scenario. The 51 cancer patients had cancer volumes ranging from 2.0-17.8 mL and had a median % free PSA of 8.9%.
An additional portion of PSA that is complexed with α 2-macroglobulin can be measured only if the complex is opened and the PSA epitopes become accessible. Of the total PSA (tPSA) in serum, 10-30% is not bound to serum proteins and is called free PSA (fPSA). Results: The mean age of the entire population was 63.6 years (range 35 to 86). Abnormal digital rectal examination findings were present in 33.4% of the patients. The mean and median values of PSA and cPSA were significantly higher and the F/T PSA ratio was lower in patients with prostate cancer. ojN9e.complexed psa vs free psa
