Background and objective: Poor assessment of asthma control results in suboptimal treatment. Identifying parameters that accurately assess control will benefit treatment decisions. The Asthma Control Test (ACT) is a five-item questionnaire for the assessment of asthma control. This study evaluated its correlation with the treatment decisions made by asthma specialists in an outpatient clinic setting, and compared its performance with other conventional parameters including spirometry, PEF rate (PEFR), fractional exhaled nitric oxide (FeNO) and BHR.
Methods: The 383 (122 men) study subjects completed a 1-month diary on symptoms and PEFR before the assessment. All subjects then completed the ACT together with same-day spirometry and FeNO measurement. BHR to methacholine was performed in 73 subjects in the week before assessment. Asthma specialists, blinded to the results of the ACT, FeNO and BHR (but not spirometry and PEFR), assessed the patients' level of control according to the 2006 version of the Global Initiative for Asthma guidelines and made appropriate treatment decision.
Results: The group mean (SD) age was 46.1 (13.4) years with pre-bronchodilator FEV(1) 84.72 (20.81) % predicted. Receiver operating characteristic (ROC) curve analysis found that an ACT score of < or = 20 best correlated with uncontrolled asthma (area under curve (AUC) = 0.76) with a sensitivity of 70.5%, specificity 76.0%, positive predictive value 76.2% and negative predictive value 70.2% for predicting step-up of asthma therapy. On ROC analysis, the ACT score had the highest AUC (0.81 (P < 0.001)) for changing asthma therapy when compared with FeNO, spirometry, PEFR and BHR parameters
Conclusions: The ACT correlated better with treatment decisions made by asthma specialists than spirometry, PEFR and FeNO.