In their otherwise excellent editorial on lower urinary tract symptoms (LUTS), Blanker et al made two surprising assertions.1 They recommend rectal examination, especially when patients fear prostate cancer, but state that its objective value is limited. I presume they mean by this that rectal examination is poor at discriminating between benign and malignant prostatic disease. I agree.
Therefore, to follow this by saying rectal examination will often meet the expectation of the patients, and (if negative) patients can be reassured that prostate cancer is not the cause of their symptoms, but one cannot state categorically that such patients do not have cancer. This sounds rather doubtful medicine; reassuring patients on an imperfect test, when there is a superior one: the prostate specific antigen (PSA).
Blanker et al reject the use of PSA in patients with LUTS by equating it with screening. This is an error; screening is systematic investigation of asymptomatic individuals, not investigation of symptomatic patients. The difference between these populations is twofold.
First, the prevalence of disease is almost certainly higher in the symptomatic population than the asymptomatic one. Most LUTS have positive predictive values for prostate cancer of around 3%, whereas the yield of cancers in asymptomatic screening is lower.2 Second, if treatment is being considered, it is likely to be different for a malignant as opposed to a benign prostate.
I wholly agree with the authors that we must inform patients about the pros and cons of PSA testing when they present with LUTS, but we must be careful to use the right information in doing so. I have no desire to have my PSA done while I’m asymptomatic, but may well ask for it once symptoms are bad enough to see my doctor about them.
- © British Journal of General Practice 2012
