ABSTRACT
BACKGROUND: The intravenous biologics infliximab and vedolizumab are effective long-term therapies for inflammatory bowel disease (IBD). Though highly effective, suboptimal adherence may result in loss of response and adverse sequelae. The extent and outcomes of suboptimal adherence with intravenous biologics, including in IBD, requires further evaluation. OBJECTIVES: To ascertain adherence to infliximab and vedolizumab infusions, and determine factors associated with poorer adherence within an IBD cohort. METHODS: A retrospective single-centre cohort study of IBD patients, assessing adherence to infliximab and vedolizumab over 2 years (July 1, 2017 to June 30, 2019) was conducted. Medical and pharmacy dispensing records were used to determine date of infusion. Adherence was assessed using the continuous, multiple interval measure of medication gaps (CMG). Objectively measured disease remission was achieved if one or more of endoscopic remission, faecal calprotectin <100 µg/mL and/or CRP <5 mg/mL occurred within 3 months of end of follow-up. Bivariate analysis and multiple linear regression elucidated factors associated with poorer adherence. RESULTS: Of 193 IBD patients, 132 (68.4%) had Crohn's disease. One hundred and thirty six (70.5%) patients received infliximab and 57 (29.5%) received vedolizumab with a median 13 [IQR 11-14] doses administered per patient over 2 years. Adherence according to CMG was similar between infliximab and vedolizumab groups (median 1.5% vs 1.2%, p = 0.31). In multiple linear regression analysis male sex, shorter IBD duration and clinic non-attendances were each associated with poorer adherence (Beta 4.69, 3.90, 3.56 respectively, p < 0.05) and objective disease remission was inversely associated with poorer adherence (Beta -3.27, p < 0.05). CONCLUSION: There was a wide range of adherence to biologic infusions in this IBD cohort with poorer adherence associated with patient related factors. Conversely, objectively measured remission was strongly associated with adherence. This emphasises the need for targeted interventions to improve adherence and monitoring, and mitigate treatment delays.
