Diagnostic accuracy of faecal calprotectin estimation in prediction of abnormal small bowel radiology

Background: Patients being investigated for symptoms of abdominal pain, diarrhoea and or weight loss often undergo small bowel radiology as part of their diagnostic workup mainly to exclude inflammatory bowel disease. Aim: To assess and compare the utility of a single faecal calprotectin estimation to barium follow through as well as conventional inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein in exclusion of intestinal inflammation. Methods: Seventy-three consecutive cases undergoing barium follow through for investigation of symptoms of diarrhoea and or abdominal pain with or without weight loss were studied. The control group comprised 25 cases with known active Crohn's disease (positive controls), 26 normal healthy volunteers (negative controls) and 25 cases of irritable bowel syndrome diagnosed by Rome II criteria. Symptoms, erythrocyte sedimentation rate and C-reactive protein were recorded at recruitment and a single stool sample assayed for calprotectin within 7 days prior to or after barium follow through. Results: The median calprotectin value in the active Crohn's group, irritable bowel syndrome group and normal volunteers was 227 mug/g of stool, 19 and 10 mug/g respectively (P < 0.0001). A faecal calprotectin above a cut-off value of 60 mug/g was able to predict all nine cases with an abnormal barium follow through as well as all six cases with a normal barium follow through but with organic intestinal disease. The negative predictive value of a single calprotectin result below 60 mug/g of stool was 100% compared with 91% each for erythrocyte sedimentation rate > 10 mm and C-reactive protein > 6 mg/L and 84% for a combination of erythrocyte sedimentation rate and C-reactive protein in predicting absence of organic intestinal disease. Conclusion: A single stool calprotectin value < 60 mug/g of stool obviates the need for further barium radiology of the small bowel, is more accurate than measurement of erythrocyte sedimentation rate or C-reactive protein and effectively excludes Crohn's disease or non-functional gastrointestinal disease.