Questionnaire of adherence to medication of hypertensive patients
CVI, hypertensive
A questionnaire was developed in a study to measure the medication adherence of hypertensive patients. For this purpose, a mixed method study was designed in two phases, including the development of the questionnaire and the evaluation of psychometrics. In the first phase, a qualitative study was designed with the steps recommended by Waltz et al. [Item’s content validity index (I-CVI) by dividing the number of experts (18 individuals) who had given that item the score of 3 or 4 by the total number of experts. The items with CVI > 0.79 were considered appropriate, those with CVI = 0.7–0.79 were revised, and the items with CVI < 0.7 were excluded [Twenty hypertensive patients evaluated the face validity of the questionnaire qualitatively and quantitatively. Difficulty and relevancy of each item was assessed in the qualitative face validity stage. The items’ impact score was calculated in quantitative face validity stage. The same hypertensive patients rated the importance of each item, scored between 1(unimportant) to 5 (very important). Impact score for each item was calculated using the following formula:“Impact score = Frequency (%) × Importance”,where “frequency” represents the number of patients rated the item 4 or 5, and “Importance” displays the average of the item on the 1–5 rating scale. The items with impact scores equal or greater than 1.5 were kept. Reliability analysis was employed using test-retest intra-class correlation index (ICC) by 30 eligible patients who asked to complete the questionnaire twice with two interval weeks. The ICC of the questionnaire was 0.83 (95% CI: 0.76–0.90, 