Clustering approach and effects of inhaled therapy on breath-fingerprint of newly diagnosed COPD patients: an e-nose based study

Background:: Chronic obstructive pulmonary disease (COPD) has several subtypes, and new approaches are required to phenotype patients and to tailor therapy. Volatile organic compounds (VOCs) are produced during cellular metabolism and reflect biochemical pathways. The study purposes to assess whether VOCs can characterize distinctive categories of newly diagnosed COPD patients and to which extent they change in response to topical therapy.Methods:: We recruited 50 outpatients with a new diagnosis of COPD based on pre and post bronchodilator spirometry. VOCs of patients, free from smoke and fast for at least 8 hours, were collected using the Pneumopipe® at the diagnosis visit and after 3 months of COPD guidelines therapy. VOCs were analyzed using a 7 quartz metalloporphyrin-covered microbalance (QMB) electronic nose. K-means cluster analysis was performed to divide subjects in 3 clusters (N:24, N:7, N:19) basing on sensor responses. Breath-fingerprints (BP) were represented by 28-dimension radarplot.Results:: BP of the three clusters, built up using QMB responses, differ: that of the second cluster, including patients free from chronic comorbidities, differs from others in shape, while the first and third differ in area, and the third cluster is composed by patients with lower MEF75 and KCO. Inhaled therapy modifies VOCs, equalizing QMB responses. Inhaled bronchodilators change the BP area, while inhaled corticosteroids modify the BP shape.Conclusions:: Naive COPD patients free from chronic comorbidities have a distinctive BP pattern. Bronchodilators and corticosteroids differently modify the BP.