Letter: faecal calprotectin for the prediction of relapse in inactive inflammatory bowel disease.

Abstract

We read with interest the article by Zhulina et al.1 In their study, 104 patients with inflammatory bowel disease (IBD) [Crohn's disease (CD) 49; ulcerative colitis (UC) 55] provided faecal samples every 3 months, and were prospectively followed up for 2 years. They found that a twofold increase in faecal calprotectin (FC) levels between two consecutive samples with the 3-month interval was associated with a twofold risk of relapse. These data suggest that longitudinal monitoring of FC is helpful in predicting relapse in IBD. The authors did not try to find a specific cut-off level of FC because there is a wide variation in FC values according to the assay used for the measurement.2 Furthermore, they suggest that the cut-off levels are disease and phenotype specific (UC, and ileal and colonic CD). We agree with them. The standardisation of FC assays is urgently needed, and method-specific cut-off values should be determined. Moreover, the optimal cut-off levels should be determined in patients with UC and CD, separately. In the discussion section, the authors stated that the predictive value of FC remained significant even when patients with CD and UC were analysed separately. In our own prospective studies, we found that FC measurement was helpful in predicting relapse in patients with inactive UC.3, 4 We also confirmed that the measurement of FC was useful to detect endoscopic inflammation in the neo-terminal ileum and to predict future clinical recurrence after ileocolonic resection for CD.5, 6 FC may also be helpful in the prediction of relapse in patients with ileocolonic CD. However, the value of FC for the screening of inflammation in the proximal ileum remains to be elucidated. It is quite difficult to investigate the relationship between FC and CD in the more proximal segments of the small bowel that are unreachable by conventional ileocolonoscopy. In this study by Zhulina et al.,1 the number of patients with CD in the ileum seemed small and, therefore, the use of FC in ileal CD cannot be rigorously evaluated. In summary, the monitoring of FC levels is helpful in the prediction of relapse in patients with inactive UC. Nevertheless, in patients with CD, especially CD in the proximal small bowel, the value of FC remains to be further investigated. Large-scale studies including patients with more proximal small bowel CD are needed. In the study by Zhulina et al.,1 FC measurements were fixed at 3-month interval. However, the optimal interval remains unknown. Serial measurement of FC may be effective in a research setting. However, it is unclear how practical this is in the real world, in terms of cost and the number of samples patients need to provide. Declaration of personal and funding interests: None.