## Abbreviations  
ACN--acetonitrile, ADH--Alcohol dehydrogenase, ADHF--Acute decompensated heart failure, AIDS--acquired immunodeficiency syndrome, AH--Alcoholic hepatitis, ALDH--aldehyde dehydrogenase, ANNs--artificial neural networks, TD--Thermal desorption, ATP--Adenosine triphosphate, AUC--area under the curves, BADD--breath analysis based disease diagnosis, CAR--Carboxen, CF--cystic fibrosis, CKD--chronic kidney disease, CO--carbon monoxide, CO2--carbon dioxide, COPD--Chronic Obstructive Pulmonary Disease, CRC--colorectal cancer, CT--computed tomography, CVDs--Cardiovascular diseases, DMPP--dimethylallyl pyrophosphate, DMA--Dimethyl amine, DNA--Deoxyribonucleic acid, DVB--Divinylbenzene, EB--exhaled breath, EBC--exhaled breath condensate, EDRF--endothelium-derived relaxing factor, EESI-MS--Extractive ElectroSpray Ionization Mass Spectrometry, FDH--formaldehyde dehydrogenase, FENO--NO fractional concentration in exhaled breath, FID--Flame ionization detector, HS-SPME--head-space solid phase micro extraction, FQDM--Fisher's Quadratic Discriminant Method, GC--gas chromatography, GC-FID--gas chromatography combined with Flame ionization detector, GC-IMS--gas chromatography combined with ion mobility spectrometer, GC-MS--gas chromatography combined with mass spectrometry, GC-TOF-MS--gas chromatography combined with time-of-flight mass spectrometry, GSH--glutathione, HCA--hierarchical clustering analysis, HF--Heart Failure, HMG-CoA reductase--3-hydroxy-3-methyl-glutaryl-CoA reductase, IBD--Inflammatory Bowel Disease, ICU--Intensive care unit, IL-4--interleukin-4, IMS--ion mobility spectrometry, iNOS--inducible NO synthase, k-NN--k-nearest neighbour, LC--Lung cancer, LDA--linear discriminate analysis, LDCT--low dose computed tomography, LOD--limit of detection, MCCV--Monte Carlo cross-validation, MDA--malondialdehydedehyde, MEPS--microextraction by packed sorbent, MLR--Multiple Linear Regressions, MVA--multivariated analysis, MS--mass spectrometry, m/z--mass to-charge ratio, NAFLD--Non-Alcoholic Fatty Liver Disease, NDDs--neurodegenerative diseases, NIR--near infrared spectroscopy, NLST--National Lung Screening Trial, N2--nitrogen, NNK--4--(methylnitrosamino)-1-(3-pyridyl)-1-butanone, NO--nitric oxide, NSCLC--Non-Small Cell Lung Carcinoma, NTD--Needle Trap Device, O2--oxygen, ODs--Onecologic diseases, ppm--parts per million, ppb--parts per billion, ppt--parts per trillion, PCA--Principal Component Analysis, PDMS--Polydimethylsiloxane, PFA--perfluoroalkoxy polymer, PLS--Partial least-square, PNN--Probabilistic neural network, POC--point of care, PTFE--polytetrafluoroethylene, PVDC--polyvinylidene chloride, PVF--polyvinyl fluoride, PTR--protontransfer reaction, PTR-MS--proton transfer reaction with mass spectrometry, PTR-TOF-MS--proton transfer reaction with time-of-flight mass spectrometry, ROC--Receiver operator characteristic, RNS--reactive nitrogen species, ROS--reactive oxygen species, SIFT-MS--Selected ion flow tube mass spectrometry, SIMCA--soft independent modelling of class analogy, SPME--solid phase micro extraction, SVM--support vector machine, S/N--signal-to-noise ratio, TD-tubes--thermal desorption tubes, TGF-b--transforming growth factor, TMA--trimethyl amine, TNF--tumour necrosis factor, TOF-MS--proton transfer reaction with time-of-flight mass spectrometry, VOCs--volatile organic compounds, WDA--weighted digital analysis  
The authors declare no conflict of interest.