Development and validation of a revised instrument to measure burden of long-term medicines use: the Living with Medicines Questionnaire version 3

Objectives

To revise the Living with Medicines Questionnaire (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 medicines users and these and a global visual analogue scale (VAS) added to the 42-item LMQ-2. Construct validity was assessed through exploratory and confirmatory factor analyses using an on-line public survey. Criterion-related validity was measured against the Treatment Satisfaction Questionnaire with Medication (TSQM-II) and the EQ-5D-5L, in patients using community pharmacies, general practices and out-patient clinics. Reliability was assessed by test-re-test using on-line 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, autonomy, constructed as medicines burden. All subscales, except autonomy, 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), 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) 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-3 instrument has acceptable construct, criterion-related and known-groups validity, and is internally consistent as a measure of medicines burden, although reliability requires further confirmation. It could be used to measure the outcome of interventions designed to reduce the burden of polypharmacy.