title: Glucose prediction by analysis of exhaled metabolites - a systematic review.
abstract: BACKGROUND
  In critically ill patients, glucose control with insulin mandates time- and blood-consuming glucose monitoring. Blood glucose level fluctuations are accompanied by metabolomic changes that alter the composition of volatile organic compounds (VOC), which are detectable in exhaled breath. This review systematically summarizes the available data on the ability of changes in VOC composition to predict blood glucose levels and changes in blood glucose levels.
  
  
  METHODS
  A systematic search was performed in PubMed. Studies were included when an association between blood glucose levels and VOCs in exhaled air was investigated, using a technique that allows for separation, quantification and identification of individual VOCs. Only studies on humans were included.
  
  
  RESULTS
  Nine studies were included out of 1041 identified in the search. Authors of seven studies observed a significant correlation between blood glucose levels and selected VOCs in exhaled air. Authors of two studies did not observe a strong correlation. Blood glucose levels were associated with the following VOCs: ketone bodies (e.g., acetone), VOCs produced by gut flora (e.g., ethanol, methanol, and propane), exogenous compounds (e.g., ethyl benzene, o-xylene, and m/p-xylene) and markers of oxidative stress (e.g., methyl nitrate, 2-pentyl nitrate, and CO).
  
  
  CONCLUSIONS
  There is a relation between blood glucose levels and VOC composition in exhaled air. These results warrant clinical validation of exhaled breath analysis to monitor blood glucose levels.
authors: Department of Intensive Care, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands ; Department of Medical Informatics, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: Jan Hendrik
authors: JH
authors: Leopold
authors: Department of Intensive Care, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: Roosmarijn T M
authors: RT
authors: van Hooijdonk
authors: Department of Respiratory Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: Peter J
authors: PJ
authors: Sterk
authors: Department of Medical Informatics, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: Ameen
authors: A
authors: Abu-Hanna
authors: Department of Intensive Care, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: Marcus J
authors: MJ
authors: Schultz
authors: Department of Intensive Care, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands ; Department of Respiratory Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
authors: Lieuwe D J
authors: LD
authors: Bos
mesh_terms: D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism*; D001944:Breath Tests / Q000379:methods; D045853:Exhalation / Q000502:physiology*; D006801:Humans; D018384:Oxidative Stress / Q000502:physiology; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D001786:Blood Glucose; D055549:Volatile Organic Compounds
keywords: Breath; Glucose; Monitoring; Volatile organic compound