Effect of a continuous measure of adherence with infliximab maintenance treatment on inpatient outcomes in Crohn's disease

Chureen T Carter,¹ Heidi C Waters,¹ Daniel B Smith^2
1Health Economics and Outcomes Research, Janssen Scientific Affairs, LLC, Horsham, PA, USA; ²Statistics, IMS Health, Watertown, MA, USA

Background: To assess the impact of a continuous measure of adherence with infliximab maintenance treatment in Crohn's disease (CD) during the first year of treatment on CD-related health care utilization, CD-related hospitalizations, inpatient costs, and length of hospital stay.
Patients and methods: A retrospective claims analysis using the IMS LifeLink Health Plan Claims Database (September 1, 2004, to June 30, 2009) was conducted. Continuous enrollment for 12 months before and 12 months after the index date was required. Patients were required to have at least two claims with an International Classification of Diseases, 9th Revision, Clinical Modification diagnosis code for CD (555.xx) pre-index and be aged ≥ 18 years at index. Patients with three infusions during the first 56 days post-index and at least one infusion following day 56 post-index were considered to have maintenance therapy. Adherence and nonadherence were defined as a medication possession ratio of ≥ 80% and < 80%, respectively.
Results: Four hundred forty-eight patients were included in the analysis (mean age, 42.6 years; 56% female; mean ± standard deviation [SD] and median number of infliximab infusions, 7.35 ± 1.60 and 8). The number of patients who met the definition of adherence was 344 (77%). CD-related health care utilization was not significantly impacted by adherence except for ancillary services and radiology. Fewer adherent patients were hospitalized compared with nonadherent patients (9% versus 16%; P = 0.03). Adherent patients had fewer mean ± SD and median days in the hospital (5.5 ± 3.4 and 5 days) compared with nonadherent patients (13.1 ± 14.2 and 8 days; P = 0.01). Mean ± SD and median hospital costs were significantly greater for nonadherent patients ($40,822 ± $49,238 and $28,864) compared with adherent patients ($13,704 ± $10,816 and $9938; P = 0.002).
Conclusion: Adherence with maintenance infliximab over 12 months was associated with lower rates of CD-related hospitalizations and inpatient costs and a shorter length of hospital stay.

Keywords: costs, Crohn's disease, hospitalization, infliximab, length of stay, medication adherence