Development and validation of the Living with Medicines Questionnaire a generic measure of patients' experiences of medicine use and associated burden

Background: Prescription medicines are a common healthcare intervention. Although medicines are often beneficial in controlling effects of disease and preventing mortality, some people have negative experiences with medicines use. Health professionals often prioritise actual or anticipated treatment benefits above any associated psychosocial or practical burdens patients may experience when using medicines. There is a need for generic, valid and reliable patient-reported tools to evaluate varying experiences of using medicines and associated burden.

Aim: This thesis focusses on instrument development, revision and validation of a novel generic patient-reported measure of prescription medicine burden, the Living with Medicines Questionnaire (LMQ).

Methods: A systematic literature review was conducted to confirm the suitability of the LMQ-1 as a relevant measure for development. This was followed by a pragmatic, iterative, mixed methodological approach, including qualitative interviews and surveys that were used in further development and validation of this instrument. Across all studies, participants were adults, using long-term prescription medicines, and were recruited face-to-face from community pharmacies, general practices, outpatient clinics and public areas in south-east England, or on-line across England. Principal components analysis of responses to the LMQ-1 enabled preliminary item reduction, and revealed gaps in the resulting 42-item version (the LMQ-2). To cover missing domains, new item generation and semi-structured, cognitive interviews led to an interim, 58-item, LMQ-2.1 ensuring that meanings of all statements were as intended. Final item reduction and confirmatory factor analyses of responses to the LMQ-2.1 established the 41-item LMQ-3 as the final agreed instrument. Criterion-related validation of the LMQ-3 ascertained relationships among medicine burden concepts, treatment satisfaction and health-related quality of life (HRQoL). Internal consistency (Cronbach's alpha) and test-retest reliability (intraclass correlation coefficients, ICCs) were also examined. LMQ-3 composite scores were used to define levels of burden, while regression analyses assessed predictors of medicine burden.

Results: The systematic review identified the original 60-item LMQ-1 as a relevant measure based on patient-generated concepts, but which required extensive modification and testing, including content addition. The final 41-item LMQ-3 instrument covers eight domains, under an overarching construct of medicine burden: interferences with day-to-day life; patient-doctor relationships and communication about medicines; lack of effectiveness; general concerns; side effects; practical difficulties; cost-related burden, and lack of autonomy/control over medicines use. Cronbach's alpha (0.61-0.90) and ICC values (0.73-0.93) were satisfactory for most subscales. Medicine burden was established as a distinct concept negatively associated with treatment satisfaction and HRQoL. Higher-level medicine burden, estimated at 10% prevalence for the English adult population, was associated with age < 65 years, unemployment, residence in areas with higher relative level of deprivation, more frequent medicine use and combinations of formulations, but was not clearly related to the number of medicines.

Conclusion: The LMQ-3 is a relatively comprehensive, valid, reliable, and interpretable measure of medicines burden suitable for use among adults using long-term medicines for any disease/condition (s) in England. The instrument could be used to identify those with high medicines burden or in studies of healthcare interventions aimed at the prevention, and/or reduction of medicine burden.