Association between serum adalimumab concentrations and endoscopic disease activity in patients with Crohn's disease

The serum trough level of adalimumab (ADA) associated with mucosal healing (MH) remains unclear. Our objective was to determine the association between ADA trough levels and the endoscopic activity in Crohn's disease.

This was a cross-sectional study including 42 patients with Crohn's disease. Endoscopic activity was assessed using the modified Rutgeerts scoring system. The primary outcome was mucosal healing, and the secondary outcomes were serum levels of C-reactive protein and albumin.

Endoscopic disease activity negatively correlated with serum ADA trough levels (Spearman's rank correlation coefficient (ρ) = -0.42, P < 0.01). MH was achieved in 14 of 42 patients (33.3%). Serum ADA trough levels were significantly higher in the MH group than in the no-MH group (ADA mean trough level, 11.7 vs 7.5 µg/mL). The proportion of patients with ADA as the first biologic was significantly higher in the MH group than in the no-MH group (85.7% vs 53.5%, P = 0.04). The ADA trough levels that were best associated with normal C-reactive protein and albumin levels were 5.57 µg/mL (odds ratio [OR] 16.0, specificity 0.80) and 6.95 µg/mL (OR 9.2, specificity 0.81), respectively. The ADA trough level that was best associated with MH was 7.9 µg/mL (OR 13.5, specificity 0.86). The endoscopic disease activity was significantly higher in the patients with ADA as the second biologic as compared with those with ADA as the first biologic (P < 0.05).

Mucosal healing requires higher ADA trough levels, compared with those required to normalization of routine clinical markers.