Calbiotech Prostate Specific Antigen(PSA) ELISA

SUMMARY AND EXPLANTION 
Prostate Specific Antigen (PSA) is a single chain glycoprotein produced by epithelial cells of the prostate gland. PSA is useful in the management of patients with prostate cancer. The measurement of serum PSA has become the most accepted test to indicate men who are at risk of having prostate cancer and who should be examined by other tests. Using a cut-off of 4 ng/ml, 92% of men over 50 years of age with malignant prostatic tissues, 8% of healthy men and 28% of men with benign prostate hyperplasia (BPH) test positive for PSA. Three major forms of PSA exist in the serum: free PSA, bound PSA and complex PSA. Bound PSA is found in higher concentrations in patients with prostate cancer; whereas, free PSA is detected in higher concentrations in patients with BPH. If the free PSA to total PSA ratio is >25%, it is unlikely that the patient has prostate cancer; whereas, if free PSA is <16% then prostate cancer is likely to be the cause. Serial measurement of PSA concentration in the serum is an important tool in monitoring patients with prostatic cancer and determining the potential and actual effectiveness of surgery or other therapies, or may allow for earlier discovery of residual or recurrent carcinoma after radical prostatectomy or radiotherapy. Current indications suggest that men over 50 years should be screened with digital rectal examination and PSA. Men with a high risk of prostate cancer, such as a family history or of African heritage, should begin annual testing at age 40 years. If both are normal, the patient can be followed with annual evaluations and monitoring to determine the rate of change. Slight elevations in PSA (4.1 ng/ml to 10.0 ng/ml) warrant a transrectal ultrasound (TRUS) to evaluate prostate volume and echogenicity of the gland. Hypo-echogenic lesions should be biopsied. Elevated PSA density (>0.15 ng/ml/cc), very high PSA (>10 ng/ml) or a free-to-total PSA ratio of <16% warrants systemic biopsy.

PRINCIPLE OF THE TEST 
The PSA ELISA kit is a solid phase assay based on a streptavidin-biotin principle. The standards, samples and a reagent mixture of Anti-PSA Enzyme and Biotin conjugates (conjugate reagent) are added into the wells, coated with Streptavidin. PSA in the patient’s serum forms a sandwich between two highly specific Anti-PSA antibodies, labeled with Biotin and HRP. Simultaneously, the biotinylated antibody is immobilized onto the well through a high affinity Streptavidin-Biotin interaction. Unbound protein and excess biotin/enzyme conjugated reagent are washed off, by washing buffer. Upon the addition of the substrate, the intensity of color developed is directly proportional to the concentration of PSA in the samples. A standard curve is prepared relating color intensity to the concentration of the PSA.

STORAGE AND STABILITY 
1. Store the kit at 2 - 8°C. 
2. Keep microwells sealed in a dry bag with desiccants. 
3. The reagents are stable until expiration of the kit. 
4. Do not expose test reagents to heat, sun, or strong light.