Persistence, adherence, healthcare resource utilisation and costs for interferon Beta in multiple sclerosis: a population-based study in the Campania region (southern Italy)

To differentiate five formulations of Interferon Beta for the treatment of multiple sclerosis (MS) in clinical practice, by analysing persistence, adherence, healthcare resource utilisation and costs at population level. In this population-based study, we included individuals with MS living in the Campania Region of Italy from 2015 to 2017, on treatment with intramuscular Interferon Beta-1a (Avonex® = 618), subcutaneous pegylated Interferon Beta-1a (Plegridy® = 259), subcutaneous Interferon Beta-1a (Rebif® = 1220), and subcutaneous Interferon Beta-1b (Betaferon® = 348; and Extavia® = 69). We recorded healthcare resource utilisation from administrative databases (hospital discharges, drug prescriptions, MS-related outpatients), and derived costs from the Regional formulary. We classified hospital admissions into MS-related and non-MS-related. Persistence (time to switch to other disease modifying treatments (DMTs)), and adherence (medication possession ratio (MPR) = medication supply obtained/medication supply expected during follow-up period) were calculated. Patients treated with Rebif® were younger, when compared with other Interferon Beta formulations (p < 0.01). The probability of switching to other DMTs was 60% higher for Betaferon®, 90% higher for Extavia®, and 110% higher for Plegridy®, when compared with Rebif® (p < 0.01). Plegridy® presented with 7% higher adherence (p < 0.01), and Betaferon® with 3% lower adherence (p = 0.03), when compared with Rebif®. The probability of MS-related hospital admissions was 40% higher in Avonex® (p = 0.03), 400% higher in Betaferon® (p < 0.01), and 60% higher in Plegridy® (p = 0.04), resulting into higher non-DMT-related costs, when compared with Rebif®. Interferon Beta formulations presented with different prescription patterns, persistence, adherence, healthcare resource utilisation and costs, with Rebif® being used in younger patients and with less MS-related hospital admissions.