Breath biomarkers could aid IPF detection
medwireNews: A number of exhaled biomarkers have the potential to discriminate between patients with idiopathic pulmonary fibrosis (IPF) and healthy controls, but further work is needed to confirm their clinical utility, say the authors of a systematic review.
In their analysis of 14 studies comprising a total of 257 IPF patients, Conal Hayton, from The University of Manchester in the UK, and colleagues identified 20 biomarkers measured in exhaled breath or exhaled breath condensate that distinguished between individuals with and without IPF.
As reported in Respiratory Research, biomarkers that were significantly elevated in samples from IPF patients versus controls included exhaled breath nitric oxide (alveolar nitric oxide concentration and fractionated exhaled nitric oxide at flow rates of 50 ml, 100 ml and 150 ml per second), as well as markers of oxidative stress in exhaled breath condensate such as hydrogen peroxide and 8-isoprostane.
On the other hand, breath condensate markers including cobalt, iron, copper and selenium were present at significantly lower levels in the IPF patients, as was p-cymene in exhaled breath.
Four of the markers – alveolar nitric oxide, 8-isoprostane, hydrogen peroxide and p-cymene – also showed correlation with measures of lung function in individual studies of IPF patients, but two studies investigating breath biomarkers among treated versus untreated IPF patients failed to demonstrate a significant association.
Although the majority of the biomarkers were only investigated in single studies, the team was able to carry out a meta-analysis of three studies investigating alveolar nitric oxide, and found that average levels were significantly higher in IPF patients than controls, at 8.5 versus 4.4 ppb.
These findings suggest that alveolar nitric oxide “may have potential as a clinical biomarker”, say Hayton and co-authors, but they caution that the meta-analysis was “limited by small sample size and significant heterogeneity”.
The researchers also note that most of the studies included in their systematic review did not include a validation cohort or longitudinal data, and the biomarkers were investigated in “a total patient cohort of less than 300 patients using a wide variety of analytical techniques”, meaning that the clinical utility of breath biomarkers in IPF remains “unclear”.
Nevertheless, they believe that “[b]reath sampling represents an attractive investigative method, being both non-invasive, simple to collect and unlimited in quantity.”
Hayton and team therefore call for “[l]arger studies with longitudinal data […] to identify biomarkers with diagnostic and prognostic potential.”
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