BACKGROUND: Faecal calprotectin is a reliable biomarker for lower gastrointestinal inflammation. However, there are limited data on the utility of calprotectin from stoma effluent. AIM: The aim of this study was to determine the performance of stomal calprotectin in identifying Crohn disease activity in those with a stoma. METHODS: Patients with Crohn disease and an ileostomy or colostomy were identified from three sites in Australia using a clinical management software. Disease activity was classified based on the presence of inflammation on imaging and/or endoscopy within 3 months of the sample. The primary outcome was the median stomal calprotectin in people with active versus inactive Crohn disease. Other clinical indices, such as C-reactive protein and Harvey Bradshaw Index, were evaluated as a surrogate biomarker for disease activity. RESULTS: Thirty stomal calprotectin results were identified for 23 patients with paired investigations. Of 30 cases, six had active disease. The median stomal calprotectin in active versus inactive disease were 17 μg/g (interquartile range (IQR) 5-211) and 61 μg/g (IQR 19-105, P = 0.38) respectively. Accordingly, stomal calprotectin demonstrated poor sensitivity for active disease (33% at cut-off of 50 μg/g). C-reactive protein was higher for active disease (25, IQR 5-199) compared with inactive disease (5, IQR 2-17, P = 0.06), but there was no difference in the Harvey Bradshaw Index (9 (IQR 7-11) vs 5 (3-7), P = 0.10). CONCLUSION: Stomal calprotectin did not reliably distinguish between active and inactive Crohn disease. C-reactive protein is a more reliable biomarker for disease activity in the setting of ileostomy/colostomy. Further prospective studies are needed to identify more robust biomarkers for detecting inflammation in stoma patients.