Issues in the assessment of PSA immunoassays

The physician and laboratorian have several proven PSA assays from which to choose, and several more are likely to achieve FDA approval soon. Furthermore, an assay that is FDA approved offers considerable reassurance that the many aspects of assay design and manufacturing processes meet an acceptable standard. This will become even more critical as assays report values in the ultrasensitive range. We have attempted to review here some of the most important issues related to PSA assay performance and standardization. Standardization particularly is a complex problem for which solutions are just now appearing. Yet efforts must continue to minimize controversies, because many more assays will be forthcoming and because newer applications of PSA determinations will place more pressure on proper assay evaluations. For example, measurement of free PSA, PSA-ACT complexes, and the ratio of one to the other are intriguing possibilities for added clinical benefit. Also, ultrasensitive PSA assays add a new dimension to the detection of residual disease and may provide unique opportunities for the implementation of new therapies and their timely evaluation. In our opinion, the impact of PSA on the management of prostate cancer is still growing, and the opportunities for better and new assays are still great.