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* = Presenting author

P145 Fecal calprotectin correlates with inflammatory disease activity as seen on CT imaging of the small bowel better than clinical assessment

G. Rosenfeld*1, J. Brown2, P. Vos2, J. Leipsic2, R. Enns3, B. Bressler3

1University of British Columbia, Medicine, Vancouver, Canada, 2University of British Columbia, Radiology, Vancouver, Canada, 3University of British Columbia, Division of Gastroenterology, Vancouver, Canada

Background

The Harvey Bradshaw Index (HBI) is a clinical index used to assess disease activity in patients with Crohn's disease (CD). The HBI may not correlate well with more objective assessments of disease activity such as endoscopic, histologic or radiologic evaluations. As a result, biomarkers such as Fecal Calprotectin (FC) have been developed which may correlate better with objective measures of disease activity. However, the validity of FC as a marker of active small bowel inflammation has been questioned. We evaluated the validity of the HBI and FC to assess for active small bowel inflammation in patients undergoing Computed Tomography Enterography (CTE) for investigation of potential CD.

Methods

FC and HBI were evaluated in patients enrolled in a CTE trial undergoing standard and low radiation dose CT scans for patients with CD. Patients referred to a tertiary IBD centre for diagnostic CTE for evaluation of potential CD, underwent a standard exam and a low dose CTE exam in a random sequence on the same day. The HBI was used to determine clinical disease activity and stool samples for FC were processed in standard fashion and analyzed using the Buhlmann Quantum BlueTM device. FC levels were reported with a range from < 100ug/g to >1800 ug/g. De-identified, randomly ordered images were reviewed by 2 experienced radiologists, independently for signs of small bowel CD and an overall assessment of "active" or "inactive" was made.

Table 1. Using a cutoff of 150 ug/g with values > 150 ug/g representing active disease, FC had a sensitivity of 0.61, specificity of 0.79, a PPV of 0.76 and an NPV of 0.62 for detecting active disease on CTE.

ASIRActiveInactive/AbsentPActiveInactive/AbsentP
HBI0.281Fecal Calprotectin<0.001
Median (IQR)3.0 (1.0, 6.0)3.0 (2.0, 8.0)254.5 (100.0, 834.0)100.0 (100.0, 131.0)
Mean (SD)4.4 (4.5)5.3 (4.9)556.8 (596.8)181.6 (222.3)
Range(0.0, 19.0)0.0, 21.0)(100.0, 800.0)100.0, 1206.0)

Average HBI and FC scores compared to CTE assessment

Results

A total of 103 patients underwent CTE scanning and had HBI and FC Results available for review. 46% of the subjects were male with mean age of 43.6 (± 15.7) years. Average HBI and FC scores are presented in (insert Table here)

Conclusion

Fecal Calprotectin accurately identifies the presence or absence of active inflammation as seen on CTE scanning in patients being evaluated for small bowel Crohn's disease while the Harvey Bradshaw index did not correlate with disease activity.