Association of airway inflammation with asthma control level evaluated by the asthma control test.

BACKGROUND

The association between airway inflammation and asthma control level is not clear at present.

OBJECTIVE

This study aimed to explore the association by using induced sputum and asthma control status as determined by the Asthma Control Test (ACT). We also evaluated the association between the scores for each ACT question item and eosinophilic or neutrophilic airway inflammation.

METHODS

The ACT and sputum induction were performed at the same time. Associations between total scores or scores for each question item and sputum eosinophil or neutrophil counts were examined. The study was approved by an Institutional Review Board.

RESULTS

Of the 101 patients with chronic asthma enrolled, data from 98 (controlled n = 66, uncontrolled n = 32) were analyzed [60.0 years (43.0-68.0) M:F = 34:64]. Current control status determined by the ACT was not significantly associated with eosinophilic or neutrophilic inflammation. Among the ACT items, only nocturnal symptoms were associated with sputum eosinophils: patients with a positive answer to the question had significantly higher eosinophil counts than patients with a negative answer [5.4 (2.2-17.6) versus 2.1 (0.7-7.3), respectively, p = 0.08]. Furthermore, significant correlation was found between eosinophil counts and the scores for nocturnal symptoms (rs = -0.218 p = 0.031). On the other hand, patients with rescue use of a short-acting b2-agonist (SABA) had significantly higher sputum neutrophil counts than non-SABA users [73.4 (52.8-83.4) versus 61.0 (36.3-74.8), respectively, p = 0.031]. The other ACT items were not significantly associated with sputum neutrophils. The neutrophil count correlated significantly with the frequency of rescue SABA use (rs = -0.218 p = 0.031).

CONCLUSIONS

Asthma control level evaluated by the ACT was not associated with airway eosinophilic or neutrophilic inflammation. However, the frequency of nocturnal symptoms was associated with sputum eosinophilia, and the frequency of rescue SABA use was associated with sputum neutrophilia.