Predicting inflammatory bowel disease in children with abdominal pain and diarrhoea: calgranulin-C versus calprotectin stool tests

Objective Calgranulin-C (S100A12) is a new faecal marker of inflammation that is potentially more specific for inflammatory bowel disease (IBD) than calprotectin, since it is only released by activated granulocytes. We compared calgranulin-C and calprotectin to see which of the two tests best predicted IBD in children with chronic abdominal pain and diarrhoea. Design Delayed-type cross-sectional diagnostic study. Setting and patients Previously undiagnosed patients aged 6-17years, who were seen in paediatric clinics in the Netherlands and Belgium, sent in a stool sample for analysis. Patients with a high likelihood of IBD underwent upper and lower endoscopy (ie, preferred reference test), while those with a low likelihood were followed for 6 months for latent IBD to become visible (ie, alternative reference test). We used Bayesian modelling to correct for differential verification bias. Main outcome measures Primary outcome was the specificity for IBD using predefined test thresholds (calgranulin-C: 0.75 mu g/g, calprotectin: 50 mu g/g). Secondary outcome was the test accuracy with thresholds based on receiver operating characteristics (ROC) analysis. Results IBD was diagnosed in 93 of 337 patients. Calgranulin-C had significantly better specificity than calprotectin when predefined thresholds were used (97% (95% credible interval (Cl) 94% to 99%) vs 71% (95% Cl 63% to 79%), respectively). When ROC-based thresholds were used (calgranulin-C: 0.75 mu g/g, calprotectin: 400 mu g/g), both tests performed equally well (specificity: 97% (95% Cl 94% to 99%) vs 98% (95% Cl 95% to 100%)). Conclusions Both calgranulin-C and calprotectin have excellent test characteristics to predict IBD and justify endoscopy.