Objectives: To revise the Living with Medicines Questionnaire version 2 (LMQ-2), which measures the burden of using prescribed medicines, to include cost and expand side effects and social issues.
Methods: New statements were developed and validated through cognitive interviews with medicine users, and these and a global visual analog scale (VAS) were added to the 42-item LMQ-2. Construct validity was assessed through exploratory and confirmatory factor analyses using an online public survey. Criterion-related validity was measured against the Treatment Satisfaction Questionnaire with Medication (TSQM-II) and the EuroQoL 5-level quality of life measure (EQ-5D-5L), in patients using community pharmacies, general practices, and outpatient clinics. Reliability was assessed by test-retest using online public distribution.
Results: The 58-item interim instrument (n=729) was reduced to 41 items after factor analysis, which confirmed an eight-domain structure: relationships with health professionals, practicalities, interferences, effectiveness, side effects, concerns, cost, and autonomy, constructed as medicine burden. All subscales, except autonomy, were loaded onto this construct and showed acceptable internal consistency. LMQ-VAS correlated with total LMQ scores (r=0.571). Criterion validation (n=422) demonstrated total LMQ scores negatively correlated with TSQM scores for global satisfaction (r=-0.616); domain scores showed similar correlations: effectiveness (r=-0.628), side effects (r=-0.597), and practicalities (r=-0.529). Total LMQ score was negatively correlated with EQ VAS (r=-0.383) and showed weak/moderate relationships with individual EQ-5D-5L dimensions. Test-retest (n=30) reliability showed intra-class correlation coefficients of 0.954 (total LMQ score), 0.733-0.929 (domain scores), and 0.789 (global item).
Conclusion: The LMQ version 3 (LMQ-3) instrument has acceptable construct, criterion-related and known-groups validity, and is internally consistent as a measure of medicine burden, although reliability requires further confirmation. It could be used to measure the outcome of interventions designed to reduce the burden of polypharmacy.
Keywords: long-term conditions; medicine burden; patient experience; polypharmacy.