PSA in prostate cancer: Criticai evaluation of clinically available assay methods

Abstract

PSA is probably the most commonly used tumour marker in oncology. The absolute tissue specificity of PSA, as well as its well-established rote in clinical decision making, nave certainly contributed to its widespread use. Nevertheless, the familiarity that comes from the frequent use of the marker prompts the need for the awareness of the impact of the methods on the interpretation of the assay results. Actually, PSA values obtained by different methods may vary. Differences may be of clinical relevance in some instances such as when evaluating a PSA value with reference to a given cut-off point or, mainly, when assessing any variation among serial samples from the same patient. This potential variability related to the method is due to the molecular heterogeneity of PSA as well as to the lack of standard reference material. The problem of the binding of PSA to circulating protease inhibitors is of major relevance. The occurrence of several PSA isoforms should also be taken into account. Both a strict standardization of the method and the preparation of a reference standard are expected to reduce the method-related variability. In the meantime, the same assay method should be used to monitor the same patient. Moreover, dose co-operation between the urologist and the clinical pathologist is mandatory in order to be aware of the methodological clues which eventually may affect the decision-making process.