STANDARDIZATION OF PSA IMMUNOASSAYS - PROPOSALS AND PRACTICAL LIMITATIONS

Many commercial immunoassays for prostate specific antigen (PSA) are available worldwide, and have been reported to give markedly different results, Development of appropriate reference materials, will help to standardize calibration and, therefore, minimize differences in values reported by these tests, In the United States, the National Committee for Clinical Laboratory Standards has formed a subcommittee to define and develop PSA reference materials, Two conferences to discuss standardization issues have also been convened at Stanford University, In these forums three models for preparing, characterizing, and valus-assigning PSA reference materials were presented, These models propose using both uncomplexed PSA (free PSA [f-PSA]) and PSA complexed to alpha(1)-antichymotrypsin (PSA-ACT), which are the immunoreactive forms of PSA in patient sera, Each of the models has both positive and negative aspects and differs in ease of preparation, matrix, and flexibility of use, Although these standard materials will be useful for bringing assays closer toward concordance, fundamental differences between equimolar- and skewed-response assays will preclude complete agreement with specimens displaying low or high proportions of f-PSA.