A substantial proportion of children and teenagers with suspected inflammatory bowel disease (IBD) referred for endoscopy do not have the disease. The investigators designed a clinical decision rule that included a calprotectin stool test to discern which patients require further investigations. The accuracy of this diagnostic strategy is 88.5% with a low risk of missing IBD cases. Although the number of negative endoscopies was reduced after introduction of this strategy, still 22% of the referred children and teenagers underwent an unnecessary invasive test. S100A12 (calgranulin C) is a cytoplasmic protein secreted exclusively by activated neutrophils and this stool marker may be more IBD-specific than calprotectin.