It's time to depolarise the unhelpful PSA‐testing debate and put into practice lessons from the two major international screening trials

Abstract

TO THE EDITOR: When I looked at the cover of the 5 April issue of the MJA, I feared finding another article focused on discrediting the prostate-specific antigen (PSA) test. Instead, I congratulate the authors, and the Journal, for presenting one of the rare balanced articles on this topic. Denham and colleagues called for an end to taking sides in the debate over PSA testing, and focused instead on helpful guidance. The problem is not whether PSA helps us find prostate cancer, but that we lack clinical tools for deciding which patients would benefit from aggressive treatment. However, the authors point out that there are two important tools that can help with this decision: low free to total PSA ratios, and rapid PSA doubling time (< 3 years). The PSA test is now one of the most sensitive, precise and highly standardised immunoassays in the clinical laboratory. The difficulty does not lie with the measurement but with its application. The Royal College of Pathologists of Australasia, together with the Urological Society of Australia and New Zealand, recently produced a monograph that discussed the appropriate use of the PSA test. It emphasised using age-related cut-offs for PSA levels, the free to total PSA ratio, and the calculation of PSA doubling time as modern tools to achieve optimal benefit from the test. The Australian Medicare Benefits Schedule (MBS) was changed in May 2009 (following a suggestion from the Urological Society of Australia and New Zealand) to improve utilisation of free to total PSA ratios. The Box indicates the per capita request rates of PSA testing (MBS item number 66655) and free to total PSA ratios (MBS item number 66659) from May 2009 to February 2010. Consistent with Denham et al’s observation that there are regional differences in the attitudes to prostate cancer, there is a twofold variation in PSA requesting and a sevenfold difference in free to total PSA ratio requesting across the Australian states. Furthermore, the relationship between the two tests is, if anything, inverse, suggesting that increased use of PSA testing is less commonly followed up by modern tools such as free to total PSA ratio. As a chemical pathologist, the appropriate clinical use of the PSA test has been a careerlong concern of mine. Even though the discoverer of PSA has labelled the test a public health disaster, recent “case–controlled” studies using PSA in an outdated approach (without free to total PSA ratios or doubling times) have shown a marginal benefit for screening. The indiscriminate use of PSA testing can be helpful to some but disastrous for others. Modern PSA tools may significantly improve management beyond these marginal effects. As always, the value of medical investigations lies in how intelligently we use them.