PSA Reagent – Jaj International

Prostate-specific antigen (PSA) measurements in serum by immunoassay are widely used in the screening, diagnosis, and monitoring of patients with prostate cancer although the lack of common reference reagents has led in the past to wide differences in estimates.

We report here the results of a WHO international collaborative study in which two preparations of PSA representative of the main immunoreacted components in serum, free PSA and PSA 90:10, and a preparation of recombinant DNA-derived PSA were assessed as potential standards for the calibration of diagnostic immunoassays for PSA.

PSA- a serine protease- is a secretory enzyme produced by the epithelium of the prostatic duct. In the healthy organism, PSA is a liquefaction of seminal plasma. As soon as PSA reaches the bloodstream, it is bound and inactivated by protease inhibitors. The most important inhibitors are a1- ant chymotrypsin  (ACT) and a2-macroglobulin (AMG). AMG completely encompasses the PSA molecule so that PSA thus bound is no longer detectable in serum. The PSA-ACT complex, however, allows for the detection of the tumor marker.

Since PSA is an organ-specific marker, its determination is increasingly used in primary diagnosis and together with digital-rectal examinations in the screening of high-risk groups, mainly in man above 50 years. Benign disorders such as prostatic hyperplasia or inflammatory processes in adjacent urogenital tissues may also lead to an increase in PSA serum levels thus reducing the specificity of the marker. The ratio between the PSA-ACT complex and free PSA is differentin BPH and prostate carcinoma (PCA).

Therefore, discrimination between benign and malignant disease is improved by the determination of the f/t PSA ratio. However, the exact f/t PSA ratio cannot be determined unless total PSA is completely, i.e. equimolarly, detected by the antibodies used in the assay. It is only this way that the f/t PSA quotient may be expressed as a constant cut-off value.

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