Diagnostic value of C-reactive protein for predicting activity level of Crohn's disease

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.

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).

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 > or =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 x N.

CRP appears useful to evaluate CD activity, especially to predict inactive or low activity CD.