Accuracy of self-reported medicines use compared to pharmaceutical claims data amongst a national sample of older Australian women

This study assessed agreement between two measures of medicine use, self-report by mail and pharmaceutical claims data, for a national sample (N=4,687) of older women aged 79 to 84 in 2005, from the Australian Longitudinal Study on Women’s Health. Medicines used for common chronic diseases in older people were selected, with pharmaceutical claims data retrieval periods of three and six months. Proportion of observed agreement between self-report and six month retrieval period ranged between 44% (nervous system medicines) and 94% (glucose lowering medicines). For three month retrieval, aspirin (35%) and folic acid (48%) had lowest agreement. Women were least able to accurately report use of nervous system medicines (sensitivity <50%), and most accurately report glucose lowering medicines use (sensitivity >80%). Specificity was consistently high across all classes, suggesting women could accurately report using a medicine. Pharmaceutical claims data can assist evaluation of judicious medicines use, changes to availability and uptake of medicines, and track medicine expenditure for chronic conditions. Over-the-counter medicines, medicines not covered by pharmaceutical subsidies and those used on an as needed basis may be best measured by self-report, as use may be underestimated using pharmaceutical claims data.