The article by Ananthakrishnan et al (Gut 2008;57:205–10) has suggested that there is increased morbidity and mortality in hospitalised patients with inflammatory bowel disease (IBD) who are concomitantly infected with Clostridium difficile compared with hospitalised IBD patients without infection. Such large epidemiological studies are powerful tools for identifying statistically significant associations, but must be tempered with caution when they attempt to explain causality. From the data presented we do not believe that it is possible to conclude that C difficile infection confers a greater risk of death in hospitalised patients with IBD. Importantly, there is no information regarding disease extent in the “infected” and “uninfected” IBD populations. It is plausible that disease extent, particularly …