試料中のTotal／Free PSAを測定するELISAキット Total / Free PSA ELISA Kit

PSA is a 33 kDa serine proteinase, isolated as a specific antigen for normal prostate tissue. Although PSA is a tissue specific protein and is not solely tumor specific, it has become the most important marker for prostate carcinoma, showing a better specificity than other biochemical markers used in this context.

Basically three major forms of PSA can be distinguished, only two of which are immunoreactive. The predominant form of PSA is a complex with α1-antichymotrypsin (ACT-PSA). Inactive free PSA (f-PSA) represents around 10-40% of the immunologically detectable PSA. The total amount of immunoreactive PSA is known as total PSA (t-PSA). PSA complexed with α- 2macroglobulin cannot be detected by immunological assays and is therefore frequently called occult PSA (o-PSA).

Current methods of screening men for prostate cancer utilize the detection of t-PSA. However, elevated serum PSA levels are frequently also attributed to benign prostatic hyperplasia, leading to a high percentage of false positive screening results. A potential solution to this problem involves the determination of free PSA levels. 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.