The validity and reliability of the Thai version of the asthma control test.

Background: The Asthma Control Test (ACT) has been widely used for the assessment of asthma control. However, it has never been validated in adult Thai asthmatic patients.

Objective: To determine the validity and reliability of the Thai version of the ACT in adult Thai asthmatic patients.

Methods: Any correlation between ACT and level of asthma controlled was determined using the Spearman's rank correlation coefficient. The ACT was carried out at 2 visits to a physician (4-12 weeks apart) to ascertain the level of reliability. Discriminant validity was determined using an area under receiver operating characteristic curve (AuROC) to identify the optimum cut-off point of the levels of control.

Results: Seventy-one asthmatic adult patients, 40 (56.3%) female with a mean age of 54.2 ± 14.7 years were enrolled. The Thai version of ACT showed an acceptable internal consistency reliability with a Cronbach's alpha = 0.75. Test-retest reliability was 0.82. There was a significant correlation between the ACT scores and GINA symptom control tool (r = 0.87, p < 0.001). An ACT ≤ 22 was used to screen "not well-controlled" asthma with a sensitivity of 96.4% and specificity of 93.0% and an ACT score ≤ 19 was used to screen "uncontrolled" asthma.

Conclusions: The Thai version of ACT is valid and a reliable tool for use in adult Thai asthmatic patients. However, the cut off points of ACT for levels of control should be changed to 22 and 19 for differentiation between well vs. partly controlled and partly vs. uncontrolled asthma, respectively.