Measuring the adherence to medication of elderly patients with heart failure: is there a gold standard?

ACE inhibitors and loop diuretics are treatments of first choice for heart failure, but patients must take their medications regularly to achieve maximum benefit. Adherence is commonly assessed using pill counts, self-report or electronic monitoring, with the latter widely considered the 'gold standard'. We assessed the concordance of these three methods in a sample of 52 elderly patients with heart failure over a six-week period. Substantial differences in adherence were found between the three methods. Adherence by self-report was very high for both ACE-I and diuretic, with little between-person variation. This was, however, uncorroborated by pill count and electronic monitoring. Closer examination of the electronic record suggested that the mean level of adherence overlooked patterns of openings more consistent with adherent behaviour. There seems to be no gold standard for measurement of adherence in this population.