Purpose: To develop a measure of medication-related quality of life (MRQoL) and to validate the measure in a hospital-based population of patients with polypharmacy.
Methods: The Medication-Related Quality of Life Scale version 1.0 (MRQoLS-v1.0) included 14 items developed on the basis of interviews with elderly patients with polypharmacy, defined as taking five or more medications simultaneously. This scale was tested in 219 outpatients (99 with polypharmacy and 120 without polypharmacy). Two measures were used to establish construct validity the Psychological Distress Checklist, for convergent validity, and the Medication Adherence Behavior Scale (MABS), for discriminant validity.
Results: The 14-item scale was found to be both reliable and valid. Internal consistency reliability evaluated using Cronbach's alpha for this scale was 0.91. Scores on the MRQoLS-v1.0 correlated statistically significantly and negatively with those on the Psychological Distress Checklist. Discriminant validity was demonstrated by low correlation with MABS, indicating that the MRQoLS-v1.0 measured concepts different from medication adherence. Significant differences in the MRQoLS-v1.0 between patients with polypharmacy and those without polypharmacy provided evidence for known-group validity.
Conclusions: The study presents a psychometric evaluation of a measure used to assess MRQoL of patients with polypharmacy. The instrument is practical to administer in clinics and provides a valuable adjunct to the outcome measurement for patients with polypharmacy. Further research on the sensitivity of this instrument to medication change in multi-medicated patients is warranted.
Keywords: Medication; Polypharmacy; Quality of life measure; Subjective well-being.