Development and Validation of a New Adherence Scale for Antiseizure Medications [ASASM]

Objective: The objective was to develop and validate a multidimensional scale that measures adherence levels to antiseizure medications and detects patients' reasons for non-adherence. Methods: A new scale was developed, namely the "Adherence Scale for Anti-Seizure Medication(s)-10 items [ASASM-10]". It consists of ten statements that cover different causes of non-adherence to antiseizure medications. The domain selection was based on a comprehensive literature review. Guidelines for constructing an effective scale were followed to write the statements. Three independent expert judges assessed the content validity of the scale. The reliability of ASASM-10 was tested using three methods: internal consistency measurement (Cronbach's alpha), Intraclass Correlation Coefficient [ICC] with a 95% Confidence Interval [95% CI], and test-retest reliability. Validity was tested using Principal Component Analysis [PCA] and a correlation coefficient. PCA was applied after measuring sampling adequacy via Kaiser-Meyer-Olkin [KMO] and Bartlett's sphericity. The Medication Adherence Rating Scale [MARS] was selected as a pre-existing self-report method for validation of this new scale. Results: A total of 162 patients completed the study scales (mean ages ± SD: 34.07 ± 10.406 years). The scale demonstrated a good internal consistency with Cronbach's alpha coefficient of 0.80 and exceeded the required value (i.e., 0.70) for the reliability of new scales. ASASM-10 showed a satisfactory ICC (95% CI) of 0.799 (0.718-0.857), p-value < 0.001. The test-retest reliability demonstrated a good correlation of ρ = 0.648, p-value < 0.001. The construct validity assessed by PCA retained four components as their eigenvalues exceeded one. The correlation coefficient demonstrated a positive moderate correlation between ASASM-10 and MARS (ρ = 0.283), p-value < 0.001. Conclusions: The present analyses provided evidence that ASASM-10 is a reliable and valid scale for evaluating patients' adherence to antiseizure medications. It is the first available scale for assessing medication adherence in patients with epilepsy that can be utilized in clinical practice and research settings.