Standardised assessment of patients' capacity to manage medications: a systematic review of published instruments

BACKGROUND: Older people are commonly prescribed complex multi-drug regimens while also experiencing declines in the cognitive and physical abilities required for medication management, leading to increased risk of medication errors and need for assisted living. The purpose of this study was to review published instruments designed to assess patients' capacity to self-administer medications. METHODS: Searches of Medline, EMBASE, CINAHL, PsycINFO, International Pharmaceutical Abstracts, Health and Psychosocial Instruments, Google, and reference lists of identified publications were conducted to identify English-language articles describing development and validation of instruments designed to assess patients' capacity to self-administer medications. Methodological quality of validation studies was rated independently against published criteria by two reviewers and reliability and validity data were reviewed. RESULTS: Thirty-two instruments were identified, of which 14 met pre-defined inclusion criteria. Instruments fell into two categories: those that used patients' own medications as the basis for assessment and those that used a simulated medication regimen. The quality of validation studies was generally low to moderate and few instruments were subjected to reliability testing. Most instruments had some evidence of construct validity, through associations with tests of cognitive function, health literacy, activities of daily living or measures of medication management or adherence. Only one instrument had sensitivity and specificity data with respect to prediction of medication-related outcomes such as adherence to therapy. Only three instruments had validity data from more than one independent research group. CONCLUSION: A number of performance-based instruments exist to assess patients' capacity to manage their own medications. These may be useful for identifying physical and cognitive barriers to successful medication management, but further studies are needed to determine whether they are able to accurately and reliably predict medication outcomes.