Costa and colleagues (Gut 2005;54:364–8) recently reported a study describing the ability of faecal calprotectin to predict relapse in the following year in patients with inflammatory bowel disease (IBD). They concluded that a calprotectin level >150 µg/g was predictive of relapse in Crohn’s disease (CD) and in ulcerative colitis (UC), but was more effective in predicting relapse in UC. Unfortunately, we believe that the authors failed to demonstrate these two points.

If faecal calprotectin >150 µg/g was clearly predictive of relapse in UC patients, this was not the case in CD (p = 0.07 and p = 0.31 for the likelihood ratio test in univariate and multivariate analyses, respectively). This may be due to the method used to determine the cut off value for calprotectin. Firstly, the receiver operating curve (ROC) method did not provide any cut off value for CD as the curve was not different from the diagonal and the confidence interval of the area under the curve included 0.5 (0.40–0.77). Secondly, the ROC curve method was not appropriate as it does not take into account the time to relapse, in contrast with the proportional hazards model used to test the predictive value of calprotectin. Classical methods related to time to relapse should have been preferred.^1,2

The assertion, both in the title and in the text, that calprotectin was …