Diagnostic Value of C-Reactive Protein for Predicting Activity Level of Crohn's Disease

Background & Aims: Measuring Crohn's disease (CD) activity is useful in clinical trials as well as in clinical practice, but each available instrument to measure such activity has some limitations. C-reactive protein (CRP) is a sensitive marker for inflammation and tissue injury. The aims of the study were: to assess the diagnostic value of low level of CRP for predicting a low CD activity, and to calculate optimal CRP cutoff value for selecting patients with moderate or high CD activity. Methods: One hundred fifty consecutive patients with active or nonactive CD were included in the study without any pre-selection criteria. CRP was measured, and CD activity was calculated by means of the van Hees index (VHI). Results: The median VHI score was 154.4 (interquartile range, 126.0-193.4), and the median CRP was 19.1 mg/L (interquartile range, 6.1-50.1 mg/L; upper limit of normal [N], 4 mg/L). Forty-nine percent of our patients had CRP >20 mg/L. CRP was significantly correlated to VHI (P = .0001). The probability that VHI was <150 if CRP was below upper limit of normal was equal to 1 (confidence interval, 0.891-1.000). The diagnostic value for CRP predicting a VHI ≥150 was high; the area under the receiver operating characteristic curve was equal to 0.844 (confidence interval, 0.783-0.906; P = .0001) with an optimal cutoff value of 21.6 mg/L, about 5 × N. Conclusions: CRP appears useful to evaluate CD activity, especially to predict inactive or low activity CD.