Ever wheeze as a predictor of cough variant asthma

Lee, Byung Jae; Min, Tae Hoon; Choi, Dong Chull

Abstract

BACKGROUND
Objective tests including the methacholine bronchial provocation test and the induced sputum examination are now crucial in the detection of causes of chronic cough. On the other hand, carefully taken history of characteristics, complications, or duration of cough are known not useful in diagnosing causes of chronic cough.
OBJECTIVES
To determine whether ever wheeze history can be an important clue in the diagnosis of cough variant asthma. METHODS: Patients with a history of cough lasting more than 3 weeks were enrolled. Patients who were current smokers, who had been receiving an angiotensin-converting enzyme inhibitor, who had basal FEV1 less than 70% of predicted value, who had adventitial sound on auscultation, or who had experienced resting dyspnea were all excluded. We divided the patients into two groups according to the ever wheeze history. The methacholine test (reference value of PC20 = 25mg/ml) and the induced sputum eosinophil percentile (reference value = 3%) were compared between the two groups. All patients were evaluated by an anatomic diagnostic protocol, and the prevalence of cough variant asthma was compared. RESULTS: Three hundred eighty-two patients (138 males and 244 females) with mean age of 48.2 years met the inclusion criteria. The mean duration of cough was 30.4 months (range, 3 weeks to 600 months). Ever wheezers were 154 (40.3%), and non-wheezers were 228 (59.7%). Ever wheeze group showed higher positive methacholine test (37.7% vs. 14.5%, p<0.001) and increased sputum eosinophils (43.5% vs 11.4%, P<.001) compared to non-wheeze group. The prevalence of cough variant asthma was significantly higher in ever wheeze group (33.8% vs. 6.1%, P<.001), and that of eosinophilic bronchitis showed similar result (13.6% vs. 4.8%, P<.01). The positive predictive value of the methacholine test was lower in non-wheeze group compared to ever wheeze group (42.4% vs 86.2%, P<.01). CONCLUSION: Ever wheeze history might be very important in suspecting cough variant asthma as a cause of chronic cough. In chronic cough patients without ever wheeze, prevalence of cough variant asthma and positive predictive value of methacholine test were low.