Background & Aims: The quantitative relationships between instruments and assays that measure clinical, endoscopic, and biologic disease activity in patients with Crohn's disease are poorly characterized. This study evaluated the correlations between the Crohn's Disease Activity Index (CDAI), the Simple Endoscopic Score for Crohn's Disease (SES-CD), serum high-sensitivity C-reactive protein (hsCRP) (both phenotype and genotype) and interleukin-6 (IL-6), and fecal calprotectin and lactoferrin. Methods: A total of 164 patients with Crohn's disease undergoing colonoscopy were enrolled. The CDAI and SES-CD scores, serum hsCRP and IL-6, CRP and IL-6 genotypes, and fecal calprotectin and lactoferrin were measured. Results: There were no significant associations between the CDAI and SES-CD scores (Spearman rank correlation coefficient, 0.15) or between the CDAI scores and the serum concentrations of hsCRP and IL-6, or the fecal concentrations of calprotectin and lactoferrin. In contrast, the serum hsCRP and IL-6 concentrations and the fecal calprotectin and lactoferrin concentrations were significantly higher in patients with more severe endoscopic disease activity (SES-CD score > 7 points) (P < .001 for all comparisons). The CRP 717 mutant homozygote and heterozygote status was associated with significantly lower concentrations of hsCRP (P = .02). There was a trend toward higher hsCRP concentrations in the CRP 286 heterozygous adenine mutant-type mutant genotype, but this did not reach statistical significance. Conclusions: Serum and fecal biomarker concentrations are associated with endoscopic but not clinical disease activity in patients with Crohn's disease. Stimulated hsCRP concentration is affected significantly by select genetic polymorphisms.
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