Inflammatory bowel disease (IBD) activity has historically been monitored based on symptoms and disease activity indices. Recently a “treat to target” strategy was reported to be associated with better outcomes. Optimizing biologic therapy based on Therapeutic Drug Monitoring (TDM) is becoming standard of care for management of IBD patients. However, there are limited data on serum infliximab (IFX) trough levels in Pediatric IBD patients on maintenance therapy
A chart review of patients on IFX at BC Children’s Hospital was performed. Demographics, CRP, ESR, albumin, PUCAI/PCDAI were recorded along with low IFX trough levels (baseline), and new trough levels following dose adjustments. A request for trough level was determined by the treating physician based clinically and by standard biomarkers of inflammation. Comparison was made between laboratory findings pre and post dose adjustment. A low IFX trough level was defined as serum level <5mg/mL. A patient was considered on maintenance therapy beyond week 14 or after dose #4. The data were analyzed using a t-test and x 2 and a p<0.05 was considered significant
One hundred and fifty-one active patients who received their first IFX infusion between Nov/08 and Jan/18 were reviewed. Forty-five patients (22.5%; 34 Crohn Disease (CD) and 11 Ulcerative Colitis (UC)) with low trough levels (<5mg/mL) on maintenance were identified. Median age at diagnosis was 10 years (IQR 8–12); Paris classification CD: A1b (73.5%) L3 (50%) L2 (41.2%) L1 (2.9%) L4a (17.6%) L4b (11.8%) p(41.2%) and B1 (97%), UC: E4 (63.6%) E3 (18.2%) and E2 (18.2%). Concomitant therapy in 82% of patients (Methotrexate 48.6%, Azathioprine 51.4%). The median number of IFX doses at baseline was 15 (IQR 10–30), median dose (mg/kg) 7.8 (IQR 5–10) with dosing interval of 7 weeks (SD 1.23). Baseline trough level was 1.9 (SD 0.97). Request for IFX trough level was based on clinical (31.1%), biochemical (31.1%) and both clinical and biochemical findings (37.8%). Ninety eight percent of patients had dose adjustments (increase dose, decreased interval, or both) with a 6.2-fold increase in trough levels (see table) This was associated with an 18.2% incremental increase in remission rate and further 11% reduction in disease activity