title: Biomarkers in adult asthma: a systematic review of 8-isoprostane in exhaled breath condensate.
abstract: We aimed to assess the evidence for the use of 8-isoprostane in exhaled breath condensate (EBC) as a biomarker in adult asthma.
  
  
  
  A systematic review and meta-analysis of EBC 8-isoprostane.
  
  
  
  We searched a number of online databases (including PubMed, Embase and Scopus) in January 2016. We included studies of adult non-smokers with EBC collection and asthma diagnosis conducted according to recognised guidelines. We aimed to pool data using random effects meta-analysis and assess heterogeneity using I2.
  
  
  
  We included twenty studies, the findings from which were inconsistent. Seven studies (n = 329) reported 8-isoprostane levels in asthma to be significantly higher than that of control groups, whilst six studies (n = 403) did not. Only four studies were appropriate for inclusion in a random effects meta-analysis of mean difference. This found a statistically significant between-groups difference of 22 pg ml-1. Confidence in the result is limited by the small number of studies and by substantial statistical heterogeneity (I2= 94).
  
  
  
  The clinical value of EBC 8-isoprostane as a quantitative assessment of oxidative stress in asthma remains unclear due to variability in results and methodological heterogeneity. It is essential to develop a robust and standardised methodology if the use of EBC 8-isoprostane in asthma is to be properly evaluated.
authors.affiliation: Norwich Medical School, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Peel
authors.forename: Christina-Jane
authors.initials: CJ
authors.lastname: Crossman-Barnes
authors.forename: Jonathan
authors.initials: J
authors.lastname: Tang
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Fowler
authors.forename: Gwyneth A
authors.initials: GA
authors.lastname: Davies
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Wilson
authors.forename: Yoon K
authors.initials: YK
authors.lastname: Loke
mesh_terms: D000328:Adult; D001249:Asthma / Q000175:diagnosis*; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests / Q000379:methods*; D016022:Case-Control Studies; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000032:analysis; D045853:Exhalation; D006801:Humans
chemical_list: D015415:Biomarkers; C075750:8-epi-prostaglandin F2alpha; D015237:Dinoprost