This finding has been exploited in the use of the ratio of free to total PSA and complexed PSA (cPSA) as a means of distinguishing between prostate cancer and BPH as a cause of an elevated PSA. (See 'Serum free and bound PSA' below and 'Complexed PSA' below.) 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. Correlation between the complex PSA/total PSA ratio and the free PSA/total PSA ratio, sensitivity and specificity of both markers for the diagnosis of prostate cancer Correlación del cociente PSA complex/PSA total con el cociente PSA libre/PSA total, sensibilidad y especificidad de ambos marcadores para el diagnóstico del cáncer de prostata☆ 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. 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. 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. fQqOwD.

complexed psa vs free psa