What is the appropriate cut-off value of CRP to predict endoscopic remission in patients with ulcerative colitis in clinical remission?

Purpose: Noninvasive markers for predicting endoscopic remission (ER) in patients with ulcerative colitis (UC) who are in clinical remission (CR) are important for the determination of appropriate treatment modality. C-reactive protein (CRP) is a surrogate marker for assessing disease activity, albeit with a low sensitivity and specificity when the cut-off value is 0.3 or 0.5 mg/dL, which is usually considered normal. The CRP test has been improved, and even fine values within the normal range can be measured. The aim of this study was to determine the appropriate cut-off value of CRP below 0.3 mg/dL for the prediction of ER in UC patients with CR.

Methods: A total of 132 patients who underwent endoscopic evaluation during CR were retrospectively reviewed. Clinical and endoscopic activity was measured using a simple clinical colitis activity index (SCCAI) and Mayo endoscopic subscore (MES). ER was defined as MES 0 or 1.

Results: In UC patients in CR, the CRP level was significantly lower in ER (0.05, 0.03-2.57) vs. non-ER (0.14, 0.03-2.81) (p < 0.001). The CRP value predicted ER [area under the curve (AUC = 0.710)] with a sensitivity of 71.4% and a specificity of 71.7% at a cut-off value of 0.09 mg/dL. In contrast, the value of normal CRP (< 0.3 mg/dL) did not show sufficient predictive value (sensitivity, 27.3%; and specificity, 90.9%).

Conclusions: In UC patients in CR, it may be helpful to lower the CRP cut-off value that predict ER other than 0.3 mg/dL, which is usually considered normal.