title: Biomarkers in asthma.
abstract: OBJECTIVE
  The purpose of this review is to highlight seminal and current literature that informs our understanding of the clinical and investigative utility of biomarkers in asthma. Biomarkers derive from a variety of sources [bronchiolar lavage (BAL), sputum, exhaled breath, and blood], and have widely variant performance characteristics, and applicability.
  
  
  RESULTS
  Increasing attention is given to biomarkers in exhaled breath, both gaseous (exhaled nitric oxide) and higher molecular weight moieties [in exhaled breath condensate (EBC)]. Current research in EBC analysis has focused on validation, standardization, and technical considerations, whereas research on exhaled nitric oxide (ENO) has moved to testing its predictive value in clinical situations. The use of advanced biostatistical techniques, and combinatorial analyses has led to additional advances in the utility of biomarkers.
  
  
  CONCLUSIONS
  To date, the best validated, and best performing biomarkers for clinical asthma appear to be measures of inflammation in induced sputum, and measures of ENO. Some trials using ENO appear particularly promising for early clinical use. EBC metrics are at present too inchoate for clinical purposes. However, not all important clinical and research questions can be addressed with sputum, EBC, or ENO metrics, leaving an important place for BAL, bronchial biopsy, and perhaps EBC measurements in the research arena.
authors.affiliation: Pulmonary and Critical Care Medicine, University of Texas Medical Branch, Galveston, Texas 77555-0568, USA.
authors.forename: Anandhi
authors.initials: A
authors.lastname: Murugan
authors.forename: Curig
authors.initials: C
authors.lastname: Prys-Picard
authors.forename: William J
authors.initials: WJ
authors.lastname: Calhoun
mesh_terms: D001249:Asthma / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D001944:Breath Tests; D018893:Bronchoalveolar Lavage; D045853:Exhalation; D006801:Humans; D017999:Leukotriene E4 / Q000652:urine; D009569:Nitric Oxide / Q000378:metabolism*; D013183:Sputum / Q000166:cytology
chemical_list: D015415:Biomarkers; D009569:Nitric Oxide; D017999:Leukotriene E4