Designing a Radioimmunometric Assay Kit for Prostate-Specific Antigen Measurement Using Polystyrene Tubes Coated By Immunochemical Method

ABSTRACT        Background and Objective: Prostate specific antigen (PSA) is considered as one of the most reliable biomarkers of cancer and other known prostate diseases. In the present study, solid phase sandwich immunoradiometric assay was used to measure the amount of PSA. In this type of measurement, a pair of anti-PSA antibodies on the solid phase and labeled with Iodine-125, participate in forming a complex with two different epitopes of PSA.        Methods: Variables such as irradiation level, modification of polymer surfaces by alcohol washing, different concentrations and volumes of antibody, incubation temperature and drying conditions that influence the direct coating process were optimized. Finally, the stability, accuracy and precision of the laboratory kit were evaluated by comparison with a foreign kit.       Results: According to the obtained results, preliminary preparations such as irradiation, tube washing and specific temperature conditions are not required during the coating process. Drying by lyophilization method does not affect the quality of coating. Antibody concentration of 2.5 μg/ml and coating volume of 800 μl were determined as the optimum conditions for coating, which had good stability within a year. Alignment of results obtained from the domestic and foreign kits for accuracy of 30 samples from patients was confirmed by T-test (sig 2-tailed= 0.993 and 95% confidence interval). The short-term and long-term precision for three control ranges (low, medium, high) were less than 0.25 and 0.33 of allowable total error (TEa = 10%), respectively.        Conclusion: The produced domestic kit has acceptable precision according to the CLIA criteria.        Keywords: Biological testing, Radioimmunometric assay, monoclonal antibody, prostate specific antigen, prostate disease.