In patients with inflammatory bowel disease (IBD) using biological therapy, non-adherence leads to anti-drug antibody formation and reduced effectiveness. Little is known about the optimal level of adherence in IBD patients on biologic therapy. We aimed to identify the association between adherence and disease flare and determine an optimal level of adherence.
We analyzed claims data for IBD patients prescribed adalimumab (ADA) and certolizumab (CZP) from the Truven Health MarketScan Commercial Claims and Encounters database from 2009 to 2013. Adherence was calculated using the medication possession ratio (MPR) from initiation until flare occurrence. A disease flare was defined as any hospitalization or new steroid prescription>90-days after drug initiation. The optimal MPR was determined using log-rank testing. The association between the optimal MPR and flare was assessed using multivariable Cox-Proportional hazards ratio.
There were 6,048 patients who were prescribed ADA (n=5,325) or CZP (n=723) for IBD. The average age was 41 years (±15) and 54% were female. The optimal MPR identified was 0.86 for ADA and 0.87 for CZP; 24% of the patients were below this level. Adjusting for age, gender, and concomitant medications at initiation, patients who were adherent above these levels had a 25% lower risk of flare for ADA (HR: 0.75, 95%CI: 0.67-0.83, P<0.01) and 41% lower risk for CZP (HR: 0.59, 95%CI: 0.46-0.76, P<0.01).
Patients who delay refills >2 days on average every 2 weeks of their subcutaneous biologics have significantly increased risk of flare. Further studies to improve adherence among those patients who consistently delay medication use are necessary.