Multiple modality approach to assess adherence to medications across time in Multiple Sclerosis

•One of few studies in MS employing multiple measures in medication adherence.•Different measures of medication adherence yielded different adherence levels.•Adherence rates to different administration routes of DMTs were similar.•Medication Possession Ratio did not fully correspond to medical files’ information.•Patients’ engagement with electronic monitoring devices needs cultivation. : Medication adherence is especially challenging in a chronic condition such as Relapsing Multiple Sclerosis (RMS). Medication adherence among persons with MS (PwMS) is usually assessed via a single measure, mostly electronic pharmacy records. : Assess medication adherence in multiple modes across time among PwMS; examine consistency across time and associations between measures. : PwMS (N = 194) were surveyed prospectively at three time points (baseline, 6 and 12 months later) and their health records and medication claims were retrospectively obtained. Adherence score was based on medication possession ratio (MPR) and two patient-reported outcome (PRO) measures. Electronic monitoring devices assessing medication adherence were also initiated. : MPR of each nonadherent PwMS, once compared to medical records containing prescription changes, was found as underestimating adherence. MPR was between the two PROs in identifying nonadherence and associations between the measures and across time was moderate (Kappa ranged 0.37–0.42). The use of electronic monitoring devices was not adopted by patients. A score indicated adherence as 66% and 64.9% at Time1 and Time 2, respectively, with 21.1% of PwMS nonadherent at both time points. Adherence did not vary significantly by DMT type. : Being a dynamic behavior, medication adherence should be repeatedly monitored by using multiple modalities and focused on in clinician-patient encounters, especially in chronic diseases such as MS, which requires long-term treatments. Applying PROs in monitoring medication adherence would facilitate implementation of Participatory Medicine and patient-centered strategies in MS care.