Trials of treatment are needed before trials of screening

would have yielded false positive results, so someone with a positive result on screening would have a 1 in 19 chance of developing clinical prostate cancer within three years.The authors do not mention this but instead invoke calculations based on population based data (not from this study) to argue that looking at men aged 60-74 would give the much more impressive specificity quoted in their conclusion.We must speculate why we are not told how many of the men aged 60-74 who were studied had : 12 times the normal median concentration of prostate specific antigen but did not get prostate cancer.The investigators must know these data, and omitting them severely damages the credibility of the conclusion.