Validity and reliability assessment of the Siriraj Asthma Control Questionnaire.

Abstract

The present study assessed the validity and reliability of the Siriraj Asthma Control Questionnaire in Asthma Clinic, Siriraj Hospital. The data of the questionnaire responses and spirometric results from 20 randomized asthmatic patients in the clinic including the record of 3 visits for each subject. The validation was performed by Kruskal-Wallis test comparing the scores with the level of asthma control determined by physicians according to GINA guideline. Internal consistency reliability was analyzed by Cronbach's alpha. Sixty questionnaires from 20 patients with age 29-73 years were analyzed. There were 40 controlled, 7 partly controlled and 13 uncontrolled visits. The scores from 5-items questionnaires and 6-items clinical score were significantly associated with the physician-diagnosed groups (i.e., controlled, partly controlled and uncontrolled groups). Median scores (min, max) were 0 (0, 5), 2 (0, 6), 4 (0, 12) respectively, (5-items, p < 0.001) and 2 (0, 7), 3 (1, 7), 6 (2,15) respectively, (6-items, p < 0.001). Internal consistency reliability of both 5-items questionnaire and 6-items clinical score were within the acceptable range (0.829 and 0.708 respectively). 5-items questionnaire is more associated with the physician diagnosed group and more consistent than 6-items clinical score. Further analysis revealed cutoff point at 2.5 to separate uncontrolled from controlled or partly controlled patient with sensitivity 76.9% and specificity 89.4% and cutoff point at 1.5 to separate uncontrolled or partly controlled from controlled patient with sensitivity 70.0% and specificity 85.0%. The validity and reliability of Siriraj Asthma Control Questionnaire is acceptable and might be used in the clinical practice and research in Thai asthmatic patients.