C-Reactive Protein-to-Albumin Ratio in Pediatric Inflammatory Bowel Disease: Associations with Disease Activity and Comparison with C-Reactive Protein Alone.

Background/Objectives: The C-reactive protein-to-albumin ratio (CAR) is an emerging biomarker of disease activity in adult inflammatory bowel disease; pediatric data remain limited. We evaluated CAR in pediatric Crohn's disease (CD) versus ulcerative colitis (UC). Methods: We retrospectively reviewed 97 consecutive pediatric patients (79 CD, 18 UC) diagnosed at a single center between 2012 and 2023. Results: CAR was higher in CD (median 10.06) than UC (0.49; p < 0.001). In CD, CAR correlated with erythrocyte sedimentation rate, fecal calprotectin, and clinical and endoscopic disease activity (all p < 0.05), differed across severity categories (p = 0.001 clinical, p = 0.003 endoscopic), and was higher without perianal disease (p = 0.005); the corresponding analyses in UC (n = 18) were underpowered and did not reach significance. Receiver operating characteristic analysis yielded an area under the curve (AUC) of 0.840 (cut-off 1.62; sensitivity 86.1%, specificity 72.2%), not exceeding that of CRP alone (AUC 0.851; DeLong p = 0.090). CAR decreased significantly from diagnosis to one-year follow-up in both remission and relapse groups (both p < 0.001). Conclusions: CAR reflects disease severity in pediatric CD and responds to treatment, but did not outperform CRP alone for distinguishing CD from UC. Its plausible value lies in activity assessment and serial monitoring rather than in diagnostic discrimination, a hypothesis that the present design cannot test.