Spirometric Changes in Bronchodilation Tests as Predictors of Asthma Diagnosis and Treatment Response in Patients with FEV1 ≥ 80% Predicted.

ABSTRACT

BACKGROUND: Many patients with mild asthma are undiagnosed and untreated due to the low diagnostic sensitivity of bronchodilation test (BDT). OBJECTIVE: To investigate whether airway reversibility in BDT and fractional exhaled nitric oxide (Feno) can predict the response to antiasthma therapy (RAT) in patients with suspected asthma. METHODS: This open-label, prospective cohort study included patients with chronic recurrent asthma symptoms, normal FEV1, and negative BDT results. Inhaled corticosteroids and long-acting ß agonists were given for 4 weeks. A positive RAT was defined as improved symptoms and an increase of more than 200 mL in FEV1 after inhaled corticosteroid/long-acting ß agonist treatment. Lung tissues from another 19 patients who underwent pneumectomy for lung nodules were also analyzed. RESULTS: Of 110 patients recruited, 102 completed the study. Patients in the positive RAT group had a higher Feno and greater absolute (Δ) and percent (Δ%) improvements in forced vital capacity, FEV1, and forced expiratory flows (FEFs) in BDT than in the negative RAT group. The area under the curves of Feno, ΔFEV1%, ΔFEF25-75% (percent improvement in FEF at 25%-75% of forced vital capacity), and ΔFEF75% (percent improvement in FEF at 75% of forced vital capacity) for positive RAT were 0.703, 0.824, 0.736, and 0.710, with cutoff values of 33 parts per billion and 3.50%, 15.26%, and 26.04%, respectively. A joint model of Feno and ΔFEV1% increased the area under the curve to 0.880. Inflammatory cytokines were higher in the lung tissues of patients with predicted positive RAT than in those with predicted negative RAT. CONCLUSIONS: ΔFEV1% in BDT together with Feno predicted a positive RAT and an asthma diagnosis in patients with a normal FEV1 and negative BDT. Evidence of pathological changes increases the credibility of the predictive model.