Suitability of an electronic reminder device for measuring drug adherence in elderly patients with complex medication.

We evaluated an electronic reminder device for detecting non-adherence in elderly patients with complex medication regimens. Randomly selected, home-living elderly patients were studied. The patients were aged over 65 years and were taking more than four drugs. Patients received an electronic reminder device which contained a GSM communications module. They were visited three times over a one-year period by a nurse who counted their medicine supply. We compared the adherence measured by the electronic device with the actual adherence measured by the pill count. Almost half of the 315 patients dropped out of the study for various reasons, so the calculations were performed on 168 patients. The adherence measured by the electronic reminder system was 79% and was 92% measured by pill count (P<0.0001). The limits of agreement estimated by a Bland-Altman analysis were -57 to +30. We also compared electronically measured adherence at morning/evening intake times with pill count adherence in the morning/evening only. For the pill count, there was almost no difference between morning and evening adherence rates (93%). For electronic measurement, adherence rates were lower in the evening (75%) than in the morning (81%). Electronic reminders were less reliable than the pill count in measuring adherence. However, the electronic system may be a useful supplement to other, more time consuming methods for measuring adherence.