title: Potential of Mass Spectrometry in Developing Clinical Laboratory Biomarkers of Nonvolatiles in Exhaled Breath.
abstract: BACKGROUND
  Exhaled breath contains nonvolatile substances that are part of aerosol particles of submicrometer size. These particles are formed and exhaled as a result of normal breathing and contain material from distal airways of the respiratory system. Exhaled breath can be used to monitor biomarkers of both endogenous and exogenous origin and constitutes an attractive specimen for medical investigations.
  
  
  BACKGROUND
  This review summarizes the present status regarding potential biomarkers of nonvolatile compounds in exhaled breath. The field of exhaled breath condensate is briefly reviewed, together with more recent work on more selective collection procedures for exhaled particles. The relation of these particles to the surfactant in the terminal parts of the respiratory system is described. The literature on potential endogenous low molecular weight compounds as well as protein biomarkers is reviewed. The possibility to measure exposure to therapeutic and abused drugs is demonstrated. Finally, the potential future role and importance of mass spectrometry is discussed.
  
  
  CONCLUSIONS
  Nonvolatile compounds exit the lung as aerosol particles that can be sampled easily and selectively. The clinical applications of potential biomarkers in exhaled breath comprise diagnosis of disease, monitoring of disease progress, monitoring of drug therapy, and toxicological investigations.
authors.affiliation: Department of Clinical Pharmacology, Karolinska University Laboratory Huddinge and Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden; olof.beck@karolinska.se.
authors.forename: Olof
authors.initials: O
authors.lastname: Beck
authors.affiliation: Occupational and Environmental Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Olin
authors.affiliation: Occupational and Environmental Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Mirgorodskaya
mesh_terms: D015415:Biomarkers / Q000032:analysis*; D001944:Breath Tests / Q000379:methods*; D019411:Clinical Laboratory Techniques; D045853:Exhalation; D006801:Humans; D013058:Mass Spectrometry; D010316:Particle Size
chemical_list: D015415:Biomarkers