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P277. Optimal C-reactive protein cutoff point for predicting hospitalization in patients with moderately active Crohn's disease

J. Colombel1, W.J. Sandborn2, E. Louis3, R. Panaccione4, R.B. Thakkar5, M.M. Castillo5, M. Yang5, J. Chao5, P.M. Mulani5

1Centre Hospitalier Universitaire de Lille, Lille, France; 2University of California, San Diego, La Jolla, CA, United States; 3University of Liège, Liège, Belgium; 4University of Calgary, Calgary, AB, Canada; 5Abbott Laboratories, Abbott Park, IL, United States

Aim: To identify high risk patients among patients with moderate Crohn's disease (CD), we explored the association between C-reactive protein (CRP) concentration and hospitalization risk for patients with moderately active CD and identified the optimal CRP cutoff point as a marker to predict CD-related hospitalization. CRP is a well-studied and commonly used laboratory marker of inflammation in CD [1]. The relationship between CRP and hospitalization risk given the same Crohn's Disease Activity Impairment (CDAI) score in patients with moderate CD has not been studied.

Materials and Methods: Data from CHARM, a 56-week, randomized, placebo-controlled trial of adalimumab maintenance therapy, were analyzed. All patients received adalimumab during a 4-week, open-label induction period; patients were then randomized to adalimumab or placebo for a 52-week double-blind period. For this analysis, only patients who were randomized to placebo at Week 4 and had moderate CD, defined as CDAI ≤300 at Week 4, were analyzed. A Cox model was applied to analyze the association between Week-4 CRP concentration and the probability of having a CD-related hospitalization during the 52-week double-blind period. Week-4 CDAI score, Week-4 steroid use, age, sex, weight, body mass index, and prior anti-tumor necrosis factor use were also adjusted in the model. Patients were censored if they switched to open-label adalimumab or dropped out. A receiver operating characteristic (ROC) curve was used to identify the optimal CRP cutoff point to best predict the 52-week CD-related hospitalization rate.

Results: The analysis population included 214 patients randomized to placebo with Week-4 CDAI ≤ 300. An elevated Week-4 CRP concentration was associated with a greater chance of CD-related hospitalization (hazard ratio = 1.24; p = 0.002). The ROC curve identified a CRP concentration of 1.41 mg/dL as the dichotomizing point (area under the curve = 0.68; sensitivity = 0.58; specificity = 0.80). Risk of CD-related hospitalization during the double-blind period was 3.4 times greater for patients with CRP concentrations ≥1.41 mg/dL at Week 4 vs. patients with a CRP concentrations <1.41 mg/dL (p = 0.015), with control for CDAI and other covariates.

Conclusions: Early CRP concentration represents a moderate to good marker to predict CD-related hospitalization for patients with moderately active CD given the same CDAI score. CRP concentration of 1.41 mg/dL was the optimal cutoff point for predicting long-term CD-related hospitalization.

1. Henriksen M, et al. Gut. 2008;57:1518–23.