Diagnostic test strategies in children at increased risk of inflammatory bowel disease in primary care

Abstract

Background: In children with symptoms suggestive of inflammatory bowel disease (IBD) who present in primary care, the optimal test strategy for identifying those who require specialist care is unclear. We evaluated the following three test strategies to determine which was optimal for referring children with suspected IBD to specialist care: 1) alarm symptoms alone, 2) alarm symptoms plus c-reactive protein, and 3) alarm symptoms plus fecal calprotectin.

Methods: A prospective cohort study was conducted, including children with chronic gastrointestinal symptoms referred to pediatric gastroenterology. Outcome was defined as IBD confirmed by endoscopy, or IBD ruled out by either endoscopy or unremarkable clinical 12 month follow-up with no indication for endoscopy. Test strategy probabilities were generated by logistic regression analyses and compared by area under the receiver operating characteristic curves (AUC) and decision curves.

Results: We included 90 children, of whom 17 (19%) had IBD (n = 65 from primary care physicians, n = 25 from general pediatricians). Adding fecal calprotectin to alarm symptoms increased the AUC significantly from 0.80 (0.67-0.92) to 0.97 (0.93-1.00), but adding c-reactive protein to alarm symptoms did not increase the AUC significantly (p > 0.05). Decision curves confirmed these patterns, showing that alarm symptoms combined with fecal calprotectin produced the diagnostic test strategy with the highest net benefit at reasonable threshold probabilities.

Conclusion: In primary care, when children are identified as being at high risk for IBD, adding fecal calprotectin testing to alarm symptoms was the optimal strategy for improving risk stratification.

Fig 1. Patient flow diagram.

Abbreviations: IBD: inflammatory bowel disease.

Fig 2. Decision curve for the three models predicting the outcome of IBD in the non-imputed dataset.

Representative interpretation of the decision curve: the purple line representing the alarm symptoms + fecal calprotectin strategy shows a net benefit of 0.16 at a threshold probability of 20%. In this instance, a threshold probability of 20% means that a general practitioner would be willing to refer 5 children to prevent a delay in diagnosis for 1 child with IBD. The net benefit of 0.16 means that this strategy would lead to the referral of 160 per 1000 children at risk, with all referrals having IBD. Abbreviations: CRP: C-reactive protein, FCal: fecal calprotectin.