The Pediatric Crohn Disease Activity Index (PCDAI) is an established and validated measure of disease activity in children with Crohn disease. However, its use in the research setting can be limited because of ambiguity of the subjective and anthropometric components of the index. Here we propose and evaluate a modified PCDAI (Mod PCDAI) consisting of the laboratory measures of the PCDAI plus C-reactive protein. This Mod PCDAI can provide an indication of disease activity because it correlates with the PCDAI, physicians' global assessment, and fecal calprotectin, and therefore may provide a suitable alternative to the PCDAI when required.