Background: Non-adherence to anti-hypertensive medications can lead to hypertension-related complications. One of the most effective preventive measures to mitigate these complications is to understand the underlying determinants of medication non-adherence using various scales. Unfortunately, existing scales for measuring non-adherence to anti-hypertensive medications have certain limitations, such as insufficient consideration of validity, dimensionality, and cultural adaptation. In response, the current study aimed to develop and validate a measure of non-adherence to anti-hypertensive medications-known as the Malaysian Anti-hypertensive Agent Non-Adherence Scale (MAANS)-for use in local hypertensive patients.
Methods: A two-phase mixed-methods approach was used. Phase 1 involved qualitative interviews with hypertensive patients from two health clinics in Kuala Lumpur, Malaysia. The themes extracted from these interviews were used to generate items for the MAANS. In Phase 2, data from 213 participants were analysed using exploratory factor analysis (EFA) to establish the scale's factor structure, thereby created the modified version of the MAANS. Confirmatory factor analysis (CFA) was then conducted on a separate dataset of 205 participants to confirm the factor structure, resulted in the final version of the MAANS. The reliability of the final MAANS version was assessed using Cronbach's alpha coefficient. The MAANS scores were used to predict subscales of the Malay version of the WHO Quality-of-Life (QOL) BREF, demonstrating the scale's predictive validity.
Results: Ten qualitative interviews yielded 73 items. The EFA produced a modified MAANS with 21 items grouped into five factors. However, the CFA retained three factors in the final scale: Perceived Non-Susceptibility, Poor Doctor-Patient Relationship, and Unhealthy Lifestyle. The final 14-item, 3-factor MAANS demonstrated moderate reliability (Cronbach's alpha coefficient = 0.64) and exhibited partial predictive validity, with the Poor Doctor-Patient Relationship and Unhealthy Lifestyle subscales significantly predicting Social QOL and Environmental QOL.
Conclusion: The MAANS is a reliable, valid, and multidimensional scale specifically developed to evaluate non-adherence to anti-hypertensive medications in local clinical settings with the potential to further the advancement of research and practice in sociomedical and preventive medicine.
Keywords: Hypertension; Medication adherence; Psychometric properties; Scale development; Scale validation.