Development of health-related quality of life questionnaire for patients on continuous drug use

Abstract

Background: Health-Related Quality of Life (HRQoL) instruments has become as a principal indicator of the effectiveness of medication treatment especially in case of lifelong therapy. Objectives: The purposes of the study were to develop a quality of life (QoL) questionnaire for Thai patients with continuous drug use (CDU-QoL) and to test the psychometric properties of the instrument. Methods: The development process comprised instrument development, expert review, factor analysis, and psychometric property test. Results: Construction of the instrument was initiated using qualitative methodology resulting in tentative ten domains and an initial pool of 42 items. Content validity was evaluated by nine experts. After pilot test, factor analysis, and psychometric property tested, the final version was 27-item CDU-QoL with five levels on a Likert scale consisting of six domains: Daily activities, mental activities, social activities, family support, adverse drug reaction, and positive outcomes. The overall coefficient alpha of this instrument was 0.922. Criterion-related validity was supported by positive correlations with Short Form Health Survey version 2.0 (SF-36v2), EuroQol 5-dimension-3-level (EQ-5D3L), and medication adherence scale. Conclusion: These analyses provide preliminary evidence that supports the validity and reliability of the CDU-QoL questionnaire for patients with continuous drug usage.