Inflammatory bowel disease: healthcare costs for patients who are adherent or non-adherent with infliximab therapy.

OBJECTIVE: Healthcare costs of inflammatory bowel disease are substantial. This study examined the effect of adherence versus non-adherence on healthcare costs in patients with inflammatory bowel disease.

METHODS: Adults who started infliximab treatment between 2006 and 2009 and had a diagnosis of inflammatory bowel disease were identified from MarketScan Databases. Medication adherence was defined as an infliximab medication possession ratio of 80% or greater in the first year. Mean treatment effects (adherence versus non-adherence) on costs in adherent patients were estimated with propensity-weighted generalized linear models.

RESULTS: A total of 1646 patients were identified. Significant variables in the model used to develop propensity weights were age, year of infliximab initiation, having Medicare coverage, presence of supplementary diagnoses, office as the place of service for infliximab initiation, prior aminosalicylate use, prior outpatient costs, number of prior outpatient visits, and number of prior colonoscopies. Mean total costs in adherent (n = 674) and propensity-weighted non-adherent (n = 972) patients were $41,713 versus $47,411 overall (p < 0.001), including $28,289 versus $14,889 for infliximab drug costs (p < 0.001), $2458 versus $17,634 for hospitalizations (p < 0.001), $7357 versus $10,909 for outpatient visits (p < 0.001), $236 versus $458 for emergency room visits (p < 0.001), and $3373 versus $3521 for other pharmaceuticals costs (p = 0.460).

LIMITATIONS: Costs associated with infliximab administration (infusions, adverse events) were captured in healthcare costs (inpatient, outpatient, and emergency room), not in infliximab costs. The influence of adherence on indirect costs (e.g., time lost from work) could not be determined. Reasons for non-adherence were not available in the database.

CONCLUSIONS: In patients who were adherent to infliximab treatment (a medication possession ratio of 80% or greater in the first year), adherence versus non-adherence was associated with lower total healthcare costs, supporting the overall value of infliximab adherence in patients with inflammatory bowel disease.