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Sputum cytokine profiling supported conflicting hypotheses for asthma, COPD
Sputum cytokine cluster analyses determined distinct and overlapping patient cohorts with asthma and chronic obstructive pulmonary disease, supporting competing hypotheses of airway disease pathogenesis, according to study results.
“There is ongoing debate between the ‘Dutch hypothesis,’ which proposes that asthma and COPD [chronic obstructive pulmonary disease] are manifestations of the same basic disease process, and the ‘British hypothesis,’ which suggests that asthma and COPD are distinct entities generated by different mechanisms,” researchers in the United Kingdom wrote.
The researchers compared clinical and physiological characteristics and sputum mediators between 86 patients with severe asthma (mean age, 54 years; 50% men) and 75 patients with moderate to severe COPD (mean age, 69 years; 70.7% men). Factor and cluster analyses on 18 sputum cytokines were used to determine biological subgroups, which were validated on independent cohorts with severe asthma (n=166) and COPD (n=58).
Severe asthma was distinguished from COPD through discriminant analysis using a combination of clinical and biological clusters.
“Factor and cluster analyses of the sputum cytokine profilers revealed three biological clusters: cluster 1: Asthma predominant, eosinophilic, high TH2 cytokines; cluster 2: asthma and COPD overlap, neutrophilic; cluster 3: COPD predominant, mixed eosinophilic and neutrophilic,” the researchers wrote.
Discriminant analysis or disease status with a binary assessment of sputum IL-1 beta expression was used to classify validation patients into the subgroups. There were similarities in the sputum cellular and cytokine profiles of the validation subgroups compared with the test subgroups.
“These findings may contribute to improved patient classification to enable stratified medicine,” the researchers concluded.
Disclosure: See the study for a full list of relevant financial disclosures.