C-Reactive Protein as a Prognostication Tool for Inflammation on Cross-Sectional Imaging and Colonoscopy in Inflammatory Bowel Disease

Introduction: CRP is a hepatic protein that can be utilized as a noninvasive biomarker for monitoring of disease activity in inflammatory bowel disease (IBD). CRP measurements are widely available and are inexpensive to obtain. The aim of this study was to evaluate if severity of inflammation based on levels of CRP is associated with the diagnostic yield of active inflammation on cross-sectional imaging (XCI: magnetic resonance imaging or computed tomography scan) or colonoscopy. Methods: Retrospective analysis of adults with an ICD-9/10 code diagnosis of IBD during hospitalization for IBD flare symptoms at a tertiary care center between January, 1 2013 to June 1,2017. Patients were stratified into groups with low, moderate, or high CRP levels on admission (< 10 mg/L, 10-100 mg/L and >100 mg/L). Active inflammation was defined by inflammation seen in terminal ileum or colon on cross-sectional imaging (XCI) or colonoscopy. Data was extracted from the institution’s integrated electronic data repository and electronic chart review. This study was approved by the institutional review board. Results: A total of 760 unique patients were analyzed of which 519 (348 CD, 160 UC, 11 indeterminate) met inclusion criteria. The cohort consisted of the characteristics outlined in Table. Of these 519 patient records, 146 (28.1%) had high-sensitivity CRP values and XCI on admission. On group stratification, 35/146 (24%) had a low CRP, 73/146 (50%) had a moderate CRP and 38/146 (26%) had a high CRP. Higher levels of CRP were associated with increased diagnostic yield of active inflammation on XCI (80% versus 86.3% versus 87.7%, P < 0.0399). Additionally, 78 patient records (15%) had high-sensitivity CRP values and colonoscopy on admission. On group stratification, 24/78 (30.8%) had a low CRP, 36/78 (46.2%) had a moderate CRP and 18/78 (23.1%) had a high CRP. Higher levels of CRP were associated with increased diagnostic yield of active inflammation on colonoscopy (66.7% versus 77.8% versus 100%, P < 0.0053). On subgroup analysis, there was no significant difference between patients with CD or UC (P < 0.5768). Conclusion: CRP is a widely available, inexpensive biomarker that can be used as a prognostication tool for active inflammation on imaging or colonoscopy during the initial work-up of IBD flare. Furthermore, it can be used to triage the initial work-up of active IBD.Table 1.: Demographics and biomarkers of initial cohort (n=519).