This high false positive rate is comparable with widely used screening tests such as the prostate specific antigen (PSA) for prostate cancer of around 30% [18–20], a condition with similar prevalence to that of frailty in the older population, and superior to the under 20% PPV of low dose CT for lung cancer [21, 22], a condition with a lower prevalence. This evidence concerns the gene KLK3 and lung cancer.