Older Australians' medication use : self-report by phone showed good agreement and accuracy compared with home visit

Objective: To ascertain the accuracy of telephone-interview method for measuring older people's medication use ("self-report by phone") by determining agreement between results from this method and from a home visit ("home inventory"). Study Design and Setting: An agreement study involving community-dwelling patients aged more than 65 years, selected from four general practices in the Hunter Region of Australia. Commonly used classes of drugs were selected for comparison. Results: Of 154 patients, 14 participants were ineligible, because they had hearing problems (9) or did not use any medicines (5). The response rate was 70% (98 of 140). The observed overall agreement and prevalence-adjusted and bias-adjusted kappa coefficients were very high for all prescribed drug categories, but lower for over-the-counter (OTC) and complementary medicines. Specificity of the self-report by phone compared with home inventory was consistently high across all drug classes. Sensitivity values were more than 89% for all drug classes but were lower for OTC and complementary medicines (74%) and paracetamol (78%). Similar patterns were found for negative predictive values. Positive predictive values were lower for drugs used on an as-needed basis. Conclusion: Measuring patient's medication use by telephone is an accurate and relatively inexpensive alternative to home-inventory methods, and has merit for use in future studies of older patients' drug use.