Validity and reliability assessment of the Siriraj Asthma Control Questionnaire.

Objective: The present study assessed the validity and reliability of the Siriraj Asthma Control Questionnaire in Asthma Clinic, Siriraj Hospital.

Material And Method: 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.

Results: 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%.

Conclusion: 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.