Assessment of fecal calprotectin, a surrogate marker of mucosal inflammation, is a promising means to monitor therapeutic response in pediatric inflammatory bowel disease, especially if the result is readily available. We tested the performance of a novel calprotectin rapid test, Quantum Blue, versus the conventional enzyme-linked immunosorbent assay in 134 stool samples from 56 pediatric patients with Crohn disease. The intraclass correlation coefficient analysis reflected good agreement (intraclass correlation coefficient 0.97 [95% confidence interval 0.95-0.98]) but agreement was better in lower values, where dilutions were not required. Using a cutoff of 100 μg/g for normal values, the percentage agreement between the 2 tests was 87%. The optimal cutoff values to guide clinical decisions in the therapy of inflammatory bowel disease have yet to be determined.