Clinical predictors of the effectiveness of tiotropium in adults with symptomatic asthma: a real-life study

Background: Long-acting muscarinic antagonist (LAMA) tiotropium improved lung function and reduced risks of exacerbation when added on to inhaled corticosteroids (ICS) with or without long-acting B-2 agonists (LABAs) in patients with uncontrolled asthma. However, studies predicting the effectiveness of tiotropium based on patients' clinical characteristics were limited. Methods: We conducted this retrospective study at a single medical center from July 2016 to July 2017, and used asthma control test (ACT) to evaluate the effectiveness of tiotropium add-on therapy in patients with uncontrolled asthma. The effectiveness was shown by an increase in ACT score from baseline of 3 or greater after 3 months of tiotropium add-on therapy. Results: Patients with uncontrolled asthma despite the use of low- or medium- to high-dose of ICS plus LABA (n=160) were analyzed. Among patients having good response (n=112, ACT score increased >= 3 points) to tiotropium (TGR group) and patients having poor response (n=48, ACT increased <3 points) to tiotropium (TPR group), their baseline characteristics including age, asthma and chronic obstructive pulmonary disease (COPD) overlap (ACO), cigarette use, initial FEV1, serum IgE level, eosinophil count, and BMI were significantly different. Univariate analysis showed that old age, ACO, cigarette use, initial FEV1 <80%, and BMI >30 were predictors of the effectiveness of tiotropium. Patients with high serum total IgE level >430 mu g/L and eosinophil count >0.6 x109/L had a negative impact on response to tiotropium. Multivariate logistic regression analysis demonstrated that the independent factor of poor response to tiotropium was high serum IgE level >430 mu g/L. Conclusions: Tiotropium add-on therapy in patients with uncontrolled asthma was effective. However, patients with serum total IgE level >430 mu g/L, were less likely to benefit from tiotropium.