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Free prostatic specific antigen in the blood
Last reviewed: 23.04.2024
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The content of free prostatic specific antigen in serum is normally more than 15% of the total prostatic specific antigen. The half-life is 7 hours.
Clinical PSA significantly increases when determining its various forms, the ratio of which corresponds to the type of pathological process taking place in the prostate gland. In the serum, the prostate specific antigen is in two forms: free and associated with various antiproteases. Most of the prostatic specific antigen is in a complex with a 1 -antichymotrypsin. An insignificant part of the prostatic specific antigen is associated with a 2- macroglobulin and is not determined by conventional ELISA methods. The level of free prostatic specific antigen varies depending on the individual characteristics of the body, and on the type of disease of the prostate gland. In prostate cancer in tumor cells, not only does the production of the prostatic specific antigen increase, but the synthesis of a 1 -antichymotrypsin increases significantly, as a result, the amount of bound and the free fraction of the prostatic specific antigen decreases as the total concentration of this antigen increases. As a result, the content of the free fraction of the prostatic specific antigen in the serum in prostate cancer is much lower than in normal and in a benign process. This is the basis for differential diagnosis of cancer and hyperplasia of this organ.
The essence of the study consists in the parallel determination of the total prostatic specific antigen and the free fraction of the prostatic specific antigen and the calculation of their ratio (free PSA / total PSA) x100%.
Determination of the free fraction of the prostatic specific antigen is indicated with an increase in the concentration of the total prostatic specific antigen in the blood. At ratios below 15%, ultrasound and biopsy are required. If this indicator is higher than 15%, follow-up and re-examination at 6 months are necessary.
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