Fecal Pancreatitis-Associated Protein: A Novel Biomarker in IBD?

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Background & Aim: IBD is characterized by recurrent episodes of inflammation. Adequate detection and monitoring of disease activity is required for optimal management. Ileocolonoscopy remains the gold standard, but is an invasive procedure with potential risk of complications. Activity indices have been well validated in clinical trials, but employ subjective parameters and do not always (correctly) reflect disease activity in daily practice. Serological markers such as Creactive protein (CRP) and Erythrocyte sedimentation rate (ESR) are widely used. Previous studies have pointed to varying sensitivity and specificity in the prediction of disease activity. The role of the fecal marker calprotectin is promising, but needs further validation. Our aim was to study the correlation between clinical activity indices and the biochemical markers CRP, ESR and calprotectin in a large prospective cohort of IBD patients in daily practice. Materials & methods: 322 consecutive IBD patients were recruited at the outpatient department and participated in a large ongoing prospective followup study. At study entry and at regular visits thereafter, clinical activity indices (Harvey Bradshaw (HB) for Crohn's disease and Simplified Clinical Colitis Activity Index (SCCAI) for ulcerative colitis), serum CRP, ESR and fecal calprotectin were assessed and correlations were calculated using Spearman's correlation. Results: 189 CD (mean age 43 years; 64% female) and 133 UC (mean age 49 years; 49% female) patients were included. Data are given from first visit (cross sectional). Median HBscore and SCCAI-score were 3 (range 0-17) and 1 (0-11), respectively. Active disease was present in 32% of CD and 28% of UC. Median CRP was 3.2 mg/l (range 0.9112) in CD and 2.4 (0.998) in UC patients. Median ESR was 12 mm/ 1h (range 2-52) in CD and 10 (2-56)in UC. Median calprotectin levels in UC were 89 μg/g (range 14-3366) and in CD patients 99 μg/g (range 14-1531). We found a weak but significant correlation of the HBscore with ESR (r= 0.19; p= 0.04), but not with CRP (r= 0.08; p= 0.28) nor with calprotectin (r= 0.09; p= 0.24). However in UC, the SCCAIscore correlated significantly with CRP (r= 0.26; p= 0.01), ESR (r= 0.28; p= 0.01) and calprotectin (r= 0.42; p= <0.01). Furthermore, ESR correlated significantly with calprotectin (r= 0.36; p= <0.01) in UC but not in CD patients. In addition, CRP and calprotectin correlated well in both CD (r= 0.36; p= <0.01) and UC patients (r= 0.43; p= <0.01). Disease location (ileum versus colon involvement) did not affect correlations in CD patients. Conclusion: In this cross sectional evaluation of a large prospective follow up cohort of IBD patients, the biochemical markers CRP, ESR and calprotectin correlate poorly with disease activity in CD but not in UC. Identification of new and sensitive non-invasive markers in CD is needed.