The most promising approach to improve the specificity of PSA, particularly in the range lower 10 ng/ml, is the measurement of molecular isoforms of PSA. These are the disengaged free PSA (fPSA) and the complexed PSA (cPSA) bound to α1-antichymotrypsin. These molecular differences explain the possibility to distinguish free from total PSA (F/T ratio). Free and complexed PSA have different clearances and significant differences between clearance of free PSA after radical prostatectomy (RP) and after open surgery for benign prostatic hyperplasia (BPH) are observed. 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. Complexed PSA test measures both PSA that is floating freely in the blood and PSA that is attached to other proteins in the blood. PSA levels rise with age, and men of different ethnicities may have naturally higher PSA levels, so discuss with your doctor what a healthy PSA level looks like for you. 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. Introduction: Prostatic tumor tissue produces a more complex form of PSA (cPSA) than free PSA (fPSA). For the early detection of prostate cancer, cPSA is supposed to be more sensitive than the ratio of fPSA and tPSA. The aim of the study was to evaluate the diagnostic value of cPSA in the early detection of malignant prostatic tumor. Many studies have explored the effect of free/total prostate-specific antigen (f/t PSA) ratio in monitoring prostate cancer. We conducted a meta-analysis to identify the accuracy of the f/t PSA ratio in the diagnosis of prostate cancer in patients who have PSA levels of 4 to 10 ng/mL. Prostate specific antigen (PSA) exists in the serum in several molecular forms that can be measured by immunodetectable assays: free PSA, PSA complexed to alpha 1-antichymotrypsin (complexed PSA) and total PSA, which represents the sum of the free and complexed forms. 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%. aG8Oaj.