Development of quality of life instrument for patients with continuous medication

Abstract

The purposes of this study were to develop a quality of life instrument in Thai patients with continuous medications use (CM-QOL) and to test the psychometric properties of the instrument. Construction of the CM-QOL was initiated using qualitative methodology involving 24 patients with chronic medications use, resulting in tentative 10 domains and an initial pool of 42 items. Content validity was evaluated by 9 experts from various disciplines. After revision based on the comments from the experts, 30 items were included in this instrument. The instrument was piloted in 30 participants, resulting in a Cronbach’s alpha coefficient of range 0.783-0.924. Later, 30-item CM-QOL and two well-established instruments: Short Form-36 version 2 (SF-36v2) and EuroQol (EQ5D3L) in Thai were tested concurrent validity in 530 patients with chronic medications use at least six months from two hospitals in Bangkok, one private and one government hospital. Psychometric testing, exploratory factor analysis (EFA) was analyzed the construct validity. Scale reliability, internal consistency, and convergent validity were explored. It was found that 27-item CM-QOL with 5 levels on a Likert scale consisted of 6 domains: daily activity disturbance, mental, social activity, family support, adverse drug reaction, and positive consequence. The overall coefficient alpha of this instrument was in range 0.782-0.912. Concurrent and convergent validity were supported by positive correlations with established instruments (SF-36v2, EQ-5D, SF-6D) and medication adherence scale. These analyses provide preliminary evidence support for the validity and reliability of the CM-QOL for patients with continuous medications use. Therefore, CM-QOL can be a useful instrument for comparison across multiple diseases in patients with continuous medications use in the future.