The PSA is not a ‘bad’ test: it is a good test, properly used.

By Alan Doherty, consultant urologist, the Birmingham Prostate Clinic

Something I consistently hear from both patients and GPs is the notion that the PSA test is a ‘bad’ test. I understand the basis of this: the measurement of the Prostate Specific Antigen (PSA) within the blood and a higher than expected level of PSA is used as an indicator of possible cancer within the prostate. It is an imprecise indicator: we know that three quarters of men with an elevated PSA level (3ng/ml or above) will not have cancer. Equally, around 15 per cent of men who are told they have a normal PSA do have cancer.

It is a test that has always produced some false positives (concern raised but no prostate cancer) and, to a lesser extent but significantly, false negatives (normal PSA result but cancer is present).

When people talk about the PSA test as a ‘blunt tool,’ usually their concern is about over-treatment. In the traditional pathway, still in practice in some areas, the next step after a raised PSA test was a trans-rectal biopsy; an assessment which is also imprecise, together with associated infection rates, discomfort and pain.

What might be termed the ‘game-changer’ is the MRI test. There been significant improvements in the quality of the imaging, but also, critically, the MRI is used before a biopsy to assess whether the biopsy is really needed. This is not new: we introduced MRI before biopsy at the Birmingham Prostate Clinic eight years ago and it has since been adopted in many other services. But the notion of the PSA test being a ‘bad test’ persists, perhaps rooted in memories of family, friends and patients who were treated on the old pathway; anxiety about the test remains.

In truth, the development of the MRI in prostate cancer assessment has addressed the issues around the PSA being a ‘bad test’. In our pathway, a raised PSA never indicates a biopsy; it flags further questions. We will consider any PSA test history, family history, undertake a prostate examination and the next step would be an MRI scan. We only proceed to a biopsy when we are very sure cancer is present and once we take this step, we will use a template biopsy approach to ensure no cancer is missed.

We have undertaken considerable work to assess the information and evaluation we gain from the MRI and how this corresponds to the biopsy result, if a biopsy is indicated. This gives us great confidence in our pathway, in MRI reporting and ultimately, that we are acting on clinically significant prostate cancer, but not over-treating. The PSA is a good test because it is usually the first flag for this process and is one piece in the jigsaw of information.