Introduction Faecal calprotectin (FC) is a stool biomarker recommended as a simple, non-invasive test to distinguish between inflammatory bowel disease (IBD) and functional bowel disorders. Despite a good correlation with colonic inflammation, FC is felt to be less accurate at identifying small bowel (SB) inflammation. Small bowel capsule endoscopy (SBCE) has a high sensitivity for detecting SB mucosal inflammation. We investigated the correlation between FC and SBCE in patients with suspected IBD.
Method We prospectively correlated the findings of SBCE with FC levels in patients under investigation for suspected IBD. Patient demographics, clinical symptoms, medications and blood parameters: haemoglobin (Hb), albumin, ESR and CRP were collected. SBCE findings including Lewis scores were analysed against FC values and final diagnosis.
Results 127 patients were included, mean age 42 years (range 18–75 years), 85 female. Presenting symptoms included: a combination of diarrhoea, abdominal pain and bloating (74%), diarrhoea alone (13%), abdominal pain alone (12%), rectal bleeding (1%). Median time from FC measurement to SBCE was 62 days. 12% had a family history of IBD, 14% were current smokers. 6 patients with a diagnosis of colonic pathology were excluded.
Results are presented in Table 1. Of the 61 patients with FC >100 µg/g, 14 (23.0%) had clinically significant SB findings (12 SB ulcers, 2 villous atrophy) and mean FC levels 468 µg/g (range 112–1010 µg/g). Overall a definitive diagnosis was made in 10 patients (9 Crohn’s disease, 1 NSAID enteropathy), the remaining 10 patients are undergoing further evaluation. FC >50 µg/g was significantly associated with clinically relevant SBCE findings (χ² p = 0.02). FC had a sensitivity 81%, specificity 40%, positive predictive value 42% and negative predictive value (NPV) 80%. Receiver operating curve analysis showed an area under the curve (AUC) of 0.626 for FC, similar to CRP (AUC 0.638) but better than ESR (AUC 0.524) and Hb (AUC 0.545). Albumin most closely correlated with an AUC 0.686. Multiple logistical regression showed serum albumin to be the only variable significantly associated with positive SBCE (p = 0.032). Lewis score significantly correlated with FC value (r = 0.793, p < 0.05).
Conclusion With a reasonable sensitivity and NPV, FC could be most effectively utilised to screen out patients where further SB investigation is unnecessary. However, in our series 1 patient with FC ≤50 µg/g had SB Crohn’s disease. Thus at best, FC can be only be recommended as an adjunct to clinical decision making, when patient factors and other biochemical parameters are also taken into account.
Disclosure of interest None Declared.