Clinicians currently rely on prostate specific antigen (PSA) measurement and digital rectal examination as frontline tests for screening and diagnosing prostate cancer. Much of the controversy surrounding the merits of the PSA test is based on uncertainty about its performance in population screening. In the linked study (doi:10.1136/bmj.b3537), Holmström and colleagues show the test’s limitations in this context.3

In the early 1990s, the PSA test was at the forefront of prostate cancer screening and a threshold of 4 µg/l was set. This value was thought to allow detection of many curable cancers, while limiting the number of false positives and the need for men to undergo further invasive tests.1 Since then the value of this threshold has been much debated because high grade prostate cancer has been found in people with levels below 4 µg/l.2

In their case-control study, Holmström and colleagues assessed the validity of PSA for predicting a subsequent prostate cancer diagnosis by record …