Assessing the relative contribution of the Asthma Control Test ™ and spirometry in predicting asthma control

Abstract

Rationale To assess the relative contribution of the Asthma Control Test ™ (ACT) and spirometry in determining asthma specialist's global assessment of patient's asthma control. Methods The ACT is a validated 5-item self-administered survey designed to assess asthma control. ACT was administered to 313 patients in the offices of asthma specialists. The specialist's global rating of asthma control after spirometry (blinded to ACT results) was also collected. Linear regression was used to assess the relative contribution of ACT scores and FEV 1 in predicting the specialist's global rating of asthma control. Three separate regression models were run. In each model the dependent variable consisted of the specialist's global rating of asthma control. Model 1 included ACT scores as the independent variable. Model 2 included FEV 1 as the independent variable. Model 3 included both ACT and FEV1 as independent variables. Results The results show that ACT scores explained significantly more variance in the specialist global rating of control than FEV 1 alone. The R 2 was 0.2746 (F=115.5 df. 1, 305, p<0.0001) for the model with ACT versus a R 2 of 0.2241 (F=88.1 df 1, 305, p<0.0001) for the model with FEV 1. The model with both ACT and FEV 1 explained the greatest amount of variance (R 2=0.3803, F=93.3 df 2, 305, p<0.0001) in the specialist global rating of asthma control. Conclusions Patient-based assessments are a valid source of information in determining asthma control. ACT provides greater predictive value in determining the patient's asthma control than FEV 1 alone, but the best strategy consists of one that uses both sources of information.