Use of antibiotic prophylaxis in clean non-implant wounds

Sir, I enjoyed reading the leading article by David Leaper entitled ‘Use of antibiotic prophylaxis in clean nonimplant wounds’. One message in particular needs to be written across the hearts and minds of all surgical specialist registrars desperate for research papers, as well as their consultant chiefs. It is that two-armed controlled trials which predict reductions in wound infection rates from 7.5% to 2.5% with a power of 80% require a total of approximately 1600 patients. Trials enrolling smaller numbers are at risk from a type II error, which means that the P value can falsely indicate non-significance at the conventional 5% level when there is actually a genuine underlying benefit from prophylaxis. We have previously expounded this point in detail in the surgical literature. Put simply, the harsh message is that a trial of 200 elective inguinal hernia cases, however meticulously carried out, is unlikely to demonstrate a genuine difference in any conceivable range of infection rates. Consequently, such trials should not be undertaken in the first place and, in the event that they are, the reports on which they are based should not be accepted for publication.