Development of the ASK-20 adherence barrier survey

Poor medication adherence is widespread among patients with chronic conditions requiring long-term drug therapy. Medication adherence is determined by multiple patient-, context-, and therapy-dependent factors. This paper describes the development and initial validation of the ASK-20 survey, created to identify actionable risk factors for medication nonadherence and to improve communication about adherence.

A pool of 30 items was generated through comprehensive literature review. Items were refined and the item pool was expanded through an expert panel review and patient focus groups to yield 47 candidate items, each with five response options ranging from either Strongly Agree to Strongly Disagree or from In the Last Week to Never. The pool of 47 candidate items was administered to a web-based sample of 605 patients taking medications and reporting a diagnosis of asthma, diabetes, or depression for psychometric testing and item reduction.

Eleven multi-item factor groupings with two additional unique items were identified on the basis of principal components analysis and interpretability. Twenty (20) items representing ten factor groupings were selected for the final instrument. Each of the final items was dichotomized as positive - indicating a barrier, or negative. Two summary scores - the sum of all positive barriers or Total Barrier Count (TBC) and the sum of raw item scores, the ASK-20 score - were calculated. Concurrent validity of the dichotomously scored individual items, the TBC and ASK-20 scores in relation to self-reported adherence was generally good. Cronbach's alpha coefficient was 0.77 for the TBC and 0.85 for the ASK-20 score.

ASK-20 consists of 20 clinically actionable items representing multiple factors that affect medication adherence. The ASK-20 survey demonstrated satisfactory validity and internal consistency and may be used to identify actionable barriers to adherence across a spectrum of chronic diseases. Future research using more objective measures of adherence is warranted to confirm the exploratory validity and reliability of ASK-20 reported in this study.