The Autobio free prostate specific antigen (f-PSA) chemiluminescence immunoassay (CLIA) kit is intended for the quantitative determination of f-PSA concentration in human serum.
Prostate Specific Antigen (PSA), a glycoprotein with a molecular weight of 34,000D, was first isolated by Wang et. al. in 1979. It is mainly found in the cytoplasm of prostate acinar cells and ductal epithelium. In addition to being present in normal tissue, PSA is also present in prostatic cancerous tissue, benign hyperplastic tissue, in prostatic fluid and seminal plasma, and is therefore a useful clinical marker for prostate cancer. Two immunoreactive forms of PSA are found in serum: free and complexed PSA. The complexed form is given by the binding of alpha-1-antichymotrypsin (ACT) to the active site of PSA. The PSA molecule which is not bound to the serine protease inhibitor ACT, named Free PSA, is found in lower concentrations than the complexed form.
Current methods of screening men for prostate cancer utilize the detection of the major PSA-ACT form. Levels of 4.0ng/ml or higher are strong indicators of the possibility of prostatic cancer. However, elevated serum PSA levels have also been attributed to benign prostatic hyperplasia and prostatitis, leading to a large percentage of false positive screening results. A potential solution to this problem involves the determination of free PSA levels. Preliminary studies have suggested that the percentage of free PSA is lower in patients with prostate cancer than those with benign prostatic hyperplasia. Thus, the measurement of free serum PSA in conjunction with total PSA, can improve specificity of prostate cancer screening in selected men with elevated total serum PSA levels, which would subsequently reduce unnecessary prostate biopsies with minimal effects on cancer detection rates.
The proportion, or percent, of free PSA determined by comparing the concentration of free PSA to the concentration of total PSA has been proposed as a way to improve the discrimination between BPH and prostate cancer, especially in those men with intermediate levels of total serum PSA.
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