BACKGROUND: Asthma is a common chronic disease affecting patients' health status and quality of life. Although recent guidelines focus on asthma control, asthma remains poorly controlled in many patients even under specialist care. Asthma Control Test™ (ACT) is a short, simple, patient-based tool that provides consistent assessment of asthma.OBJECTIVE: The aim of this study was to estimate the relationship of ACT with objective measures of lung function and inflammation such as forced expiratory volume in 1st second (FEV(1)) and exhaled nitric oxide (FeNO) in outpatients admitted for initial diagnosis of asthma and at follow-up.METHODS: One hundred and sixty (104 women and 56 men, mean age 39.7 ± 16.6 years) asthmatic patients with newly diagnosed asthma were included in the study. Patients completed the ACT questionnaire and underwent a detailed clinical examination, FeNO measurement, and prebronchodilator spirometry before (visit 1) and 4-12 weeks after initiation of treatment (visit 2).RESULTS: At visit 1, the mean ACT score was 21.27 ± 3.74. According to ACT score, 37 patients (23.1%) were completely controlled, 85 patients (53.1%) were partly controlled, and 38 patients (23.8%) were uncontrolled. Patients with uncontrolled asthma had statistically higher FeNO values than patients with partly controlled (p = .038) and completely controlled asthma (p = .016). ACT score was found to have a positive correlation with prebronchodilator %FEV(1) (r = 0.177, p = .025) and negative correlation with FeNO ( r = -0.211, p = .007). At visit 2, the mean ACT score was 23.00 ± 2.19. The change in ACT score between the two visits was significantly correlated to changes in FEV(1) (r = 0.538, p < .001) and in FeNO (r = -0.466, p < .001). Patients treated with inhaled corticosteroids (ICSs) showed significant improvement in FEV(1) and in ACT score and a decrease in FeNO compared with patients without ICS treatment.CONCLUSION: Although FEV(1) remains the main objective parameter for evaluating asthma, ACT score was found to reflect lung function and inflammation in a Greek asthmatic population.