Infliximab trough level (ITL) severely affects therapeutic outcomes of Crohn's disease (CD) patients under infliximab (IFX). Recently, frontier research has focused on identifying ITL based on different therapeutic targets. Although previous studies have elaborated clinical value of ITL monitoring on short-term outcomes in CD patients during therapy, studies contraposing the predictive value of ITL on long-term endoscopic outcomes in CD patients are still scarce domestically and overseas.
To explore the predictive value of ITL in combination with inflammatory biomarkers on long-term endoscopic outcomes in CD with clinical remission during IFX maintenance therapy.
CD patients with endoscopic remission under long-term IFX maintenance therapy in the First Affiliated Hospital of Zhejiang Chinese Medicine University from January 2012 to December 2020 were collected. ITL and inflammatory biomarkers were continuously monitored during the therapy. The Step I study was conducted from weeks 14 to 54 of IFX treatment. The Step II study was conducted from weeks 54 to 108 of IFX treatment. Endoscopic outcomes were defined as endoscopic activity (Crohn's disease endoscopic index of severity score > 2 points or Rutgeerts score > i1) and endoscopic remission (Crohn's disease endoscopic index of severity score ≤ 2 points or Rutgeerts ≤ i1). Endoscopic relapse free survival was defined as endoscopic remission at the beginning of the study stage and maintaining endoscopic remission during the study stage.
At week 14, low ITL [odds ratio (OR) = 0.666, 95% confidence interval (CI): 0.514-0.862, 
Combination of ITL, CRP, and FCP contribute to long-term endoscopic prognosis monitoring. During IFX maintenance treatment, low ITL, high CRP level, and high FCP level were independent risk factors of CD patients with clinical remission in adverse endoscopy outcomes within 1-year follow-up.