Changing pattern of sputum cell counts during successive exacerbations of airway disease

BACKGROUND: Exacerbations of airway disease are eosinophilic, neutrophilic, both or neither, and this determines the treatment needed. We examined changes in the cellular nature of airway inflammation between consecutive exacerbations and their predictors in individual patients. METHODS: In a retrospective survey of 1786 consecutive sputum cell counts from 1139 patients with airway disease, we identified 79 patients with two or more exacerbations at an interval of >or=6 weeks. The patients were divided into those who demonstrated a change in the type of airway inflammation and those who did not. RESULTS: There were 186 exacerbations of airway disease over 22 months. The cellular nature of inflammation was eosinophilic in 43%, neutrophilic in 40%, combined eosinophilic and neutrophilic in 5% and unclassified in 12%. A change in the type of airway inflammation was seen in 38 patients (48%). Patients, whose previous exacerbation was eosinophilic or neutrophilic were twice or nearly three times more likely, respectively, to have a subsequent exacerbation of the same type. There was no significant difference in the time to the second exacerbation or the inflammatory type of the second exacerbation in relation to the first exacerbation, irrespective of the cellular nature of the first exacerbation. CONCLUSIONS: Quantitative sputum cell counts during successive exacerbations identify that they are commonly of different type, reflecting different causes and the need for different treatment. Their use, when available, helps to optimize therapy.