Optimal cut-off value and clinical usefulness of the Adherence Starts with Knowledge-12 in patients with asthma taking inhaled corticosteroids

Background: Non-adherence to inhalation regimens is common in asthmatic patients. The Adherence Starts with Knowledge-12 (ASK-12) survey was developed to detect and address patient-specific barriers to medication adherence. Our objective is to investigate the clinical usefulness of the ASK-12 for assessing and addressing adherence to inhalation therapy in asthma. Methods: The ASK-12 was administered to 138 asthmatic patients. Using pharmacy-refill data, we examined the cut-off value of the ASK-12 to identify patients who were non-adherent to inhalation regimens and identify factors associated with non-adherence. To verify the usefulness of the ASK-12, inhalation regimens were prospectively switched to less-expensive and simpler (once-daily) dosing regimens in eight non-adherent asthmatic patients who reported specific-barriers in "inconvenience of twice-daily inhaler use" and "cost". Results: Valid responses were received from 114 (82.6%) patients. A significant correlation was found between pharmacy-refill rates and the ASK-12 total score (r=-0.55, P < 0.0001). The optimal cut-off value of the ASK-12 total score to discriminate non-adherent patients (defined by pharmacy-refill rate < 80%) was 23, with 71.4% specificity and 93.3% sensitivity. Using this value, 52 (45.6%) patients were classified as non-adherent. Univariate followed by multivariate analysis identified younger age as a predictor of non-adherence to inhalation regimens (odds ratio, 2.67; 95% CI, -0.95 to -0.06; P=0.027). Switching inhaled medicines in eight patients resulted in significant improvements in both ASK-12 scores and asthma control. Conclusions: The ASK-12 is a brief, practical, and clinically useful measure for assessing and addressing adherence to inhalation regimens in asthma.