Determination of concentration free PSA in the test kit Vitrotest® PSA Free is based on on a solid-phase “sandwich” ELISA followed by the use of biotin-streptavidin interaction.
○ ТК105 – 96 tests
- Solid phase: breakable microplate ELISA is coated with monoclonal antibodies specific to human PSA.
- Biotinylated anti-PSA antibody solution: biotinylated monoclonal antibodies to human PSA.
- Streptavidin-HRP conjugate: streptavidin solution conjugated with horseradish peroxidase.
- Chromogen: ready to use TMB solution.
- Volume of sample for analysis: 25 μl.
- Assay time: 1 hour.
A valuable biomarker for prostate cancer, which is now widely used for population screening, diagnosis, and monitoring of patients with prostate cancer, is the prostate-specific antigen (PSA). Screening for this tumor marker was introduced in the 1990s in the USA, Canada, Japan, and the UK, where a subsequent trend of decreased prostate cancer mortality has been observed.
Prostate-specific antigen is a glycoprotein produced by the epithelial cells of the prostate gland, the urethral mucosa, and the Cowper’s glands. PSA is secreted into the seminal fluid, ensuring semen liquefaction, but is typically found in very low concentrations in the blood. In blood serum, PSA is present in various forms: complexed with α1-antichymotrypsin (70-90%), free PSA not bound to serum proteins (10-30%), and bound to alpha-2-macroglobulin.
In men’s blood serum, the normal concentration of total PSA does not exceed 4 ng/ml. Elevated levels of this tumor marker may indicate a risk of prostate cancer. According to the American Cancer Society, the likelihood of prostate cancer with serum total PSA levels of 4-10 ng/ml is 25%, while with concentrations above 10 ng/ml, this figure approaches 50%. An increase in PSA levels can also be observed with prostate hypertrophy and prostatitis. Therefore, when elevated serum PSA levels are detected, a digital rectal examination (DRE) of the prostate is recommended to differentiate pathological conditions.
For laboratory identification of prostate cancer, the measurement of total and free prostate-specific antigen in blood serum is used. When PSA concentration is in the range of 4 to 10 ng/ml, determining the percentage of free PSA can be helpful in deciding whether a prostate biopsy is necessary. Typically, a biopsy is recommended when the percentage of free PSA is below 10%, although some doctors consider a threshold level of 25%.
The serum PSA level is an informative marker not only for screening patients for prostate cancer but also for monitoring treatment effectiveness and prognosis after surgical intervention.