Predictors of Adherence Using Panel Survey Data from Multiple Sclerosis Patients Currently Treated with High-Dose High-Frequency Interferons

Background: Treatment adherence is important for optimizing patient care in multiple sclerosis (MS).

Objectives: To evaluate the relationship between treatment with high-dose, high-frequency interferons and adherence among MS patients.

Methods: A random sample of relapsing-remitting MS patients (age ≥18 years, clinical trial-naïve) from the US National Health and Wellness Survey or Lightspeed Research panel completed an Internet survey in Nov/Dec 2012. Adherence was evaluated among those indicating current treatment (≥4 months) with subcutaneous interferon beta-1a (scIFNB1a) three times weekly (tiw) or subcutaneous interferon beta-1b (scIFNB1b) every other day (eod). Adherence was measured using the 4-item Morisky Medication Adherence Scale (forget to take medication, careless at times about taking, stop if better, stop if worse; high adherence=all negative responses). Baseline characteristics were compared using Chi-square and t-tests. Logistic regression evaluated the relationship between scIFNB1a or scIFNB1b treatment and the odds of having high adherence. Covariates included age, sex, exercise, and therapy-related variables (months on therapy, satisfaction, perception of effectiveness, cost).

Results: Of 969 surveyed, 80 scIFNB1a and 63 scIFNB1b patients met inclusion criteria (mean [standard deviation] age: 49.0 [10.4] years, 88.8% female vs 51.3 [8.7] years, 87.3% female, respectively; p-values >0.05). A greater percentage of scIFNB1a patients reported high adherence compared with scIFNB1b patients (58.8% vs 33.3%, p=0.0025). After adjusting for covariates, scIFNB1a patients had a greater odds of high adherence (odds ratio [OR] 2.92; p=0.0101). Male sex (OR 4.37; p=0.0297), time since last relapse (years; OR 1.04; p=0.0483), frequent exercise (OR 1.06; p=0.0094), and Patient-Determined Disease Steps score (OR 1.34; p=0.0110) were predictive of high adherence.

Conclusions: In this exploratory analysis, treatment with scIFNB1a tiw was strongly associated with high adherence relative to scIFNB1b eod.