Development and validation of an instrument for measuring the burden of medicine on functioning and well-being: the Medication-Related Burden Quality of Life (MRB-QoL) tool.

OBJECTIVE: Medication-related burden (MRB) is a negative experience with medicine, which may impact on psychological, social, physical and financial well-being of an individual. This study describes the development and initial validation of an instrument specifically designed to measure MRB on functioning and well-being-the Medication-Related Burden Quality of Life (MRB-QoL) tool.

METHODS: An initial pool of 76-items for MRB-QoL was generated. The link to MRB-QoL survey was sent to a sample of consumers living with at least one chronic medical condition and taking ≥3 prescription medicines on a regular basis. Exploratory factor analysis (EFA) was used to determine the underlining factor structure. Internal consistency (Cronbach's α) and construct validity were examined. The latter was examined through correlation with Medication Regimen Complexity Index (MRCI), Drug Burden Index (DBI) and Charlson's Comorbidity Index (CCI).

RESULTS: 367 consumers completed the survey (51.2% male). EFA resulted in a 31-item, five-factor solution explaining 72% of the total variance. The five subscales were labelled as 'Routine and Regimen Complexity' (11 items), 'Psychological Burden' (six items), 'Functional and Role Limitation' (seven items), 'Therapeutic Relationship' (three items) and 'Social Burden' (four items). All subscales showed good internal consistency (Cronbach's α 0.87 to 0.95). Discriminant validity of MRB-QoL was demonstrated via its correlations with MRCI (Spearman's r -0.16 to 0.08), DBI (r 0.12 to 0.28) and CCI (r -0.23 to -0.15). Correlation between DBI and 'Functional and Role Limitation' subscale (r 0.36) indicated some evidence of convergent validity. Patients with polypharmacy, multiple morbidity and DBI >0 had higher median scores of MRB-QoL providing evidence for known group validity.

CONCLUSIONS: The MRB-QoL V.1 has good construct validity and internal consistency. The MRB-QoL may be a useful humanistic measure for evaluating the impact of pharmaceutical care interventions on patients' quality of life. Future research is warranted to further examine additional psychometric properties of MRB-QoL V.1 and its utility in patient care.