Background: The dimensionality of the Asthma Control Test (ACT) was examined in two counterview studies. Up to now, the ACT has not been validated for the Greek asthma patients.
Objective: The present study was designed to examine the validity and reliability of the ACT responses in Greek asthma outpatients under a specialist's care.
Study design: Following evidence for sample-specific validity, the ACT (n = 100) was examined through construct, cross-sectional, convergent, and discriminant validity as well as internal consistency and test-retest reliability [root mean squared error of approximation (RMSEA)].
Results: A one-factor solution fit the data [χ(2) (chi-square) = 3.899, df (degrees of freedom) 5, ns, RMSEA <0.001]. The ACT showed a high internal consistency (Cronbach alpha = 0.72) and a high 2 months test-retest reliability (IR = 0.85) for the total sample. Significant differences were found between the five categories of asthma control patients (not controlled at all, poorly controlled, somewhat controlled, well controlled, and completely controlled), according to the specialists' rating, for the ACT (p < .001). Significant differences were found between patients with and without asthma control (p = .001), patients of different gender (p = .05), educational status (p = .05), mean year income (p = .01), body mass index (p = .05), follow-up visits (p = .01), as well as among patients of different age (p < .001) and severity (p < .001). An ACT score of 19 or less provided optimum balance of sensitivity (98.46) and specificity (88.57) for screening 'not controlled' asthma. Cross-sectional validity testing showed moderate correlation of the ACT score with FEV1% predicted (r = 0.57, p < .001) and disability (r = -0.42, p < .001) and moderately high correlation with dyspnea (r = -0.71, p < .001). Convergent validity testing showed that the ACT score was correlated with the specialists' rating (r = 0.89, p < .001).
Conclusion: The ACT is valid and reliable in Greek outpatients with asthma under a specialist's care.