Various laboratory biomarkers have been studied in inflammatory bowel disease (IBD) as diagnostic aids, indicators of disease activity or severity, and to predict the risk of relapse in those patients in remission. These biomarkers have enormous potential implications for patient management. For example, therapeutic decisions could be directed more appropriately if a marker could reliably distinguish active IBD from other inflammatory or non-inflammatory causes of symptoms, or if one could distinguish Crohn’s disease from ulcerative colitis. In addition, a simple, inexpensive, sensitive, specific marker could help monitor response in the clinic and in clinical trials. Finally, the ability to reliably predict the risk of recurrence would help direct appropriate therapy to those who would most likely benefit from it and avoid the expense and potential toxicity of chronic maintenance therapy in those who have a low risk of recurrence. In the current issue of Gut, Costa and colleagues¹ addressed the latter issue by studying the role of faecal calprotectin as a marker of risk of relapse in ulcerative colitis and Crohn’s disease (see page 364). Calprotectin represents 50–60% of neutrophilic cytosolic protein, is stable in faeces for several days after excretion, and has a relatively easy to perform assay which is available commercially and correlates well with the more difficult and more expensive indium 111-labelled leucocyte excretion²

Costa and colleagues¹ studied 38 patients with Crohn’s disease and 41 with ulcerative colitis in remission for a mean of five months. A baseline faecal calprotectin level greater than 150 μg/g had a sensitivity for predicting relapse within the next year of 89% in ulcerative colitis and 87% in Crohn’s disease. The specificity …