Measuring Patients' Knowledge About Adverse Effects of Angiotensin-Converting Enzyme Inhibitors

Knowledge about adverse effects of medications is an important part of proper medication use and prerequisite for good treatment adherence.

The aim of our study was to construct, develop, and test a new questionnaire for the measurement of patients' knowledge about adverse drug reactions of angiotensin-converting enzyme (ACE) inhibitors.

The 8-item questionnaire was constructed to measure adverse reactions to ACE inhibitors. The questions were closed, with 7 offered answers, in the form of a Likert scale. It was tested for psychometric properties on patients who visited their general practitioners at state-owned health facilities in 5 Serbian cities: Belgrade, Kragujevac, Banja Luka, Gracanica, and Despotovac.

The questionnaire was tested on 259 patients from general practice, taking an ACE inhibitor for more than 3 months. Experience with at least 1 adverse effect of ACE inhibitor was reported in 64 patients (24.7%), only 94 patients (36.3%) previously received any form of information about at least 1 adverse effect of ACE inhibitors from health workers, and only 42% expressed knowledge of any adverse events. The patients who were informed knew about the following adverse events as phrased in the official patient information leaflets: severe dizziness or light-headedness (44%); cough (37%); swelling of the hands, face, lips, or tongue (32%); indigestion (22%); headache (51%); and difficulty in breathing (15%). The questionnaire showed satisfactory internal consistency, with Cronbach α of 0.767, and individual scores correlated with general education of the patients. Factorial analysis revealed 2 domains (subscales): the first one with 5 questions is directed to adverse effects the patients may physically experience directly, whereas the second with 3 questions measures knowledge about adverse effects that could be experienced only indirectly, through conditions caused by the adverse effects.

The questionnaire about knowledge of ACE inhibitors' adverse effects is a reliable and probably valid instrument for measuring patients' knowledge about adverse effects of ACE inhibitors.