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Metabolites 2014, 4(2), 300-318; doi:10.3390/metabo4020300

Short-Term Intra-Subject Variation in Exhaled Volatile Organic Compounds (VOCs) in COPD Patients and Healthy Controls and Its Effect on Disease Classification

1
Welsh Centre for Printing and Coating, and Centre for Nano Health, College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP, UK
2
Department of Computer Science, Institute of Maths, Physics and Computer Science, Aberystwyth University, Aberystwyth SY23 3DB, UK
3
Institute of Life Science, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK
4
Respiratory Unit, Prince Philip Hospital, Hywel Dda University Health Board, Llanelli SA14 8QF, UK
Current affiliation: Respiratory Department, Monklands General Hospital, Airdrie ML6 0JS, UK
*
Author to whom correspondence should be addressed.
Received: 26 February 2014 / Revised: 31 March 2014 / Accepted: 29 April 2014 / Published: 9 May 2014
(This article belongs to the Special Issue Breath Analysis in Metabolomics)
View Full-Text   |   Download PDF [318 KB, uploaded 9 May 2014]   |  

Abstract

Exhaled volatile organic compounds (VOCs) are of interest for their potential to diagnose disease non-invasively. However, most breath VOC studies have analyzed single breath samples from an individual and assumed them to be wholly consistent representative of the person. This provided the motivation for an investigation of the variability of breath profiles when three breath samples are taken over a short time period (two minute intervals between samples) for 118 stable patients with Chronic Obstructive Pulmonary Disease (COPD) and 63 healthy controls and analyzed by gas chromatography and mass spectroscopy (GC/MS). The extent of the variation in VOC levels differed between COPD and healthy subjects and the patterns of variation differed for isoprene versus the bulk of other VOCs. In addition, machine learning approaches were applied to the breath data to establish whether these samples differed in their ability to discriminate COPD from healthy states and whether aggregation of multiple samples, into single data sets, could offer improved discrimination. The three breath samples gave similar classification accuracy to one another when evaluated separately (66.5% to 68.3% subjects classified correctly depending on the breath repetition used). Combining multiple breath samples into single data sets gave better discrimination (73.4% subjects classified correctly). Although accuracy is not sufficient for COPD diagnosis in a clinical setting, enhanced sampling and analysis may improve accuracy further. Variability in samples, and short-term effects of practice or exertion, need to be considered in any breath testing program to improve reliability and optimize discrimination. View Full-Text
Keywords: COPD; Exhaled volatile organic compounds (VOC); variation; machine learning COPD; Exhaled volatile organic compounds (VOC); variation; machine learning
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Phillips, C.; Mac Parthaláin, N.; Syed, Y.; Deganello, D.; Claypole, T.; Lewis, K. Short-Term Intra-Subject Variation in Exhaled Volatile Organic Compounds (VOCs) in COPD Patients and Healthy Controls and Its Effect on Disease Classification. Metabolites 2014, 4, 300-318.

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