Total PSA ELISA

GWB-F8000C

Prostate Specific antigen (PSA) is a serine protease with chymotrypsin-like activity. The protein is a single chain glycoprotein with a molecular weight of 28. 4 kDA. PSA derivesits name from the observation that it is a normal antigen of the prostrate but is not found in any other normal or malignant tissue. PSA is found in benign malignant and metastatic prostrate cancer. Since prostate cancer is the second most prevalent form of male malignancy the detection of elevated PSA levels plays an important role in the early diagnosis. Serum PSA levels have been found too more useful than prostatic acid phosphatase (PAP) in the diagnosis and management of patients due to increased sensitivity. In this method PSA calibrator patient specimen or control is first added to a streptavidin coated well. Biotinylated monoclonal and enzyme labeled antibodies (directed against distinct and different epitopes of PSA) are added and the reactants mixed. Reaction between the various PSA antibodies and native PSA forms a sandwich complex that binds with the streptavidin coated to the well. After the completion of the required incubation period the enzyme- PSA antibody bound conjugate is separated from the unbound enzyme-PSA conjugate by aspiration or decantation. The activity of the enzyme present on the surface of the well is quantitated by reaction with a suitable substrate to produce color. The employment of several serum references of known prostate specific antigen (PSA) levels permits the construction of a dose response curve of activity and concentration. From comparison tothe dose response curve an unknown specimen\' s activity can be correlated with PSA concentration. Principles of the assay: In this method standards patient specimens and/or controls (containing the native tPSA antigen) are first added to streptavidin coated wells. Biotinylated monoclonal and enzyme labelled antibodies are then added and the reactants are mixed: these antibodies have high affinity and specificity and are directed against distinct and different epitopes of tPSA. Storage and Stability: The closed reagents are stable up to the expiry date stated on the label when stored at 2. . . 8 & deg; C in the dark. Opened reagents are stable for 60 days when stored at 2?8& deg; C. Limitations of the Test: Bacterial contamination or repeated freeze-thaw cycles of the specimen may affect the absorbance values. References Christensson A Laurell CB Lilja H. Eur J Biochem 194 755- 63 (1990). Watt KW et. al. Proc Nat Acad Sci USA 83 3166-70 (1986). Chen Z Prestiglacomo A Stamey T. Clin Chem 41 1273-82 (1995). Wild D The Immunoassay Handbook. Stockton Press p452 (1994). Junker R Brandt B Zechel C Assmann G Clin Chem 43 1588- 94 (1997). Prestigiacomo AF Stamey TA ? Physiological variations of serum prostate antigen in the (4-10 ng/ml) range in male volunteers. ? J. Urol (1996); 155:1977-80. Stamey TA McNeal JE Yemoto CM Sigal BM Johnstone IM ?Biological determinants of cancer progression in men with prostate cancer. ? JAMA (19999; 281:1395-1400. Chen Z Prestigiacomo A Stamey T ?Purification and characterization of Prostate Specific Antigen (PSA) Complexed to a1- Anticymotrypsin:Potential reference Material for International Standardization of PSA Immunoassays. ? Clin Chem. (1995); 41/9:1273-1282. Horton GL Bahnson RR Datt M Cfhan KM Catalona WJ and Landenson JH. ?Differences in values obtained with two assays of Prostate Specific Antigen. ? J. Urol. (1988); 139:762-72. Stenman UH Leinonen J Alfthan H Rannikko S Tuhkanen Kand Alfthan O. ?A complex between prostate specific antigen anda1-anticymotrypsin is the major form of prostate specific antigenin serum of patients with prostate cancer:assay of complex improves clinical sensitivity for cancer. ? Cancer Res. (1991); 51:222-26.