Diagnostic Accuracy of Fecal Calprotectin for Pediatric Inflammatory Bowel Disease in Primary Care: A Prospective Cohort Study

Abstract

Purpose: In specialist care, fecal calprotectin (FCal) is a commonly used noninvasive diagnostic test for ruling out inflammatory bowel disease (IBD) in children with chronic gastrointestinal symptoms. The aim of this study was to evaluate the diagnostic accuracy of FCal for IBD in symptomatic children in primary care.

Methods: We studied 2 prospective cohorts of children with chronic diarrhea, recurrent abdominal pain, or both: children initially seen in primary care (primary care cohort) and children referred to specialist care (referred cohort). FCal (index test) was measured at baseline and compared with 1 of the 2 reference standards for IBD: endoscopic assessment or 1-year follow-up. Physicians were blinded to FCal results, and values greater than 50 μg/g feces were considered positive. We determined specificity in the primary care cohort and sensitivity in the referred cohort.

Results: None of the 114 children in the primary care cohort ultimately received a diagnosis of IBD. The specificity of FCal in the primary care cohort was 0.87 (95% CI, 0.80-0.92). Among the 90 children in the referred cohort, 17 (19%) ultimately received a diagnosis of IBD. The sensitivity of FCal in the referred cohort was 0.99 (95% CI, 0.81-1.00).

Conclusions: The findings of this study suggest that a positive FCal result in children with chronic gastrointestinal symptoms seen in primary care is not likely to be indicative of IBD. A negative FCal result is likely to be a true negative, which safely rules out IBD in children in whom a primary care physician considers referral to specialist care.

Keywords: calprotectin; child; inflammatory bowel disease; practice-based research; primary health care; sensitivity and specificity.

Figure 1

Patient flow in the study. Note: The group of children who were mainly seen in primary care and selected for referral to specialist care based on ≥1 red flags were evaluated in both analyses. Fecal calprotectin was not measured in 14 children because no stool sample was collected (9 children), the sample was not stored (2 children), or the sample of feces was too small (3 children). Two children with no stool sample were evaluated in both analyses.

Figure 2

Flow charts and contingency tables for the calculation. of diagnostic accuracy in the primary care cohort and referred cohort, using the nonimputed data set. FCal = fecal calprotectin; GI = gastrointestinal; IBD = inflammatory bowel disease; PPV = positive predictive value; NPV = negative predictive value. Note: The left flow chart shows the specificity of FCal (>50 μg/g) for IBD in the primary care cohort (11 missing values). Specificity of standard follow-up and endoscopy were 0.88 (95% CI, 0.80–0.93) and 0.50 (95% CI, 0.09–0.91), respectively. The right flow chart shows the test characteristics of FCal (>50 μg/g) for IBD in the referred cohort (5 missing values). Sensitivity of the reference standards of follow-up and endoscopy were 1.00 (95% CI, 0.34–1.00) and 1.00 (95% CI, 0.78–1.00), respectively; values for specificity were 0.87 (95% CI, 0.76–0.93) and 0.67 (95% CI, 0.35–0.88), respectively.