Low baseline alanine aminotransferase is associated with primary non-response to infliximab induction in pediatric Crohn's disease: a retrospective cohort study.

Background: Low alanine aminotransferase (ALT) has been associated with unfavorable inflammatory and nutritional phenotypes, but its relationship with infliximab (IFX) response in pediatric Crohn's disease (CD) is uncertain. Methods: We retrospectively studied 116 children with CD who received IFX induction at weeks 0, 2, and 6 and underwent response assessment at approximately week 14. Low ALT was defined as <10 U/L using a rounded, data-informed working threshold. Primary non-response (PNR) required concurrent clinical non-response, biochemical activity, and objective endoscopic or cross-sectional imaging evidence and was independently adjudicated by two pediatric gastroenterologists blinded to baseline ALT. Firth logistic regression assessed the association between low ALT and PNR after adjustment for baseline SES-CD, IFX dose, and concomitant immunomodulator use. Results: Fifty-eight children (50.0%) had low ALT and 21 (18.1%) had PNR. PNR occurred more often with low ALT (27.6% vs. 8.6%; Conclusion: Low baseline ALT was associated with PNR to IFX in pediatric CD. This exploratory association and the 10-U/L working threshold require external validation and should not guide treatment decisions in isolation.