Assessing usability of the "Adherence Starts with Knowledge 20" (ASK-20) questionnaire for Japanese adults with bronchial asthma receiving inhaled corticosteroids long term.

BACKGROUND: Maintaining high treatment adherence levels is critical for effective management of chronic diseases. The Adherence Starts with Knowledge 20 (ASK-20) questionnaire is the only linguistically validated patient-reported treatment adherence tool available in Japan. We conducted additional analyses on ASK-20 data from Japanese adults with asthma.

METHODS: This was a prospective, non-interventional, single-visit, multi-centre study in Japanese adults (n = 300) with asthma receiving long-term treatment with inhaled corticosteroids (ICS) or ICS/long-acting beta-agonists. We tested the reliability, validity and the relationship between different adherence conditions and ASK-20 score. At one centre, ICS adherence prescription rate was calculated retrospectively based on 2-year percentage ICS adherence data contained within medical records.

RESULTS: The ASK-20 had good internal consistency reliability (Cronbach's alpha = 0.76; n = 290). Discriminant validity was demonstrated with significant correlations between the percentage ICS adherence rates and both the mean ASK-20 total score and mean total barrier count (TBC) (r = -0.51 and -0.58, p < 0.001; n = 111). The ASK-20 total score discriminated between subjects with good and poor adherence measured by patients' reported questionnaire and between those of high and low percentage ICS adherence rates. All other factors that possibly affect adherence were correlated with the mean ASK-20 total score and mean TBC in addition to the number of medicines taken every day.

CONCLUSIONS: The Japanese ASK-20 is a reliable tool for assessing possible medication adherence barriers and adherence behaviour in Japanese adults with asthma. Furthermore, our results are comparable with those obtained using the ASK-20 in the United States.