Validation of Biomarkers of Exposure and Host Response
Status:
Completed
Trial end date:
2007-09-01
Target enrollment:
Participant gender:
Summary
The proposed study will evaluate biomarkers measured in exhaled breath condensate (EBC) for
the purpose of assessing clinical strategies of harm reduction. It will take advantage of a
recently developed device that permits collection of exhaled breath condensate reproducibly,
with minimal subject effort and with no oral contamination. The major goal of the trial is to
provide evidence to validate biomarkers in EBC.
This will be accomplished by collecting samples from asymptomatic smokers before and after
inducing a change in their smoking habit (cessation or reduction) with the aid of partial
nicotine replacement.
Measures to be made in EBC include H2O2, the most widely explored biomarker in this "body"
fluid. Methods that reliably can quantify levels in normal non-smokers and in asymptomatic
smokers will be used. Two fold increases in smokers have been reported by in several reports
and confirmed in preliminary data by the investigators. In addition, other biomarkers of
oxidant stress: TBARs, 8-isoprostane and nitrotyrosine will be quantified using standard
methods.
Biomarkers quantified in EBC will be assessed for reliability (i.e. reproducibility and for
sensitivity) to change and for validity (by comparison to clinically defined endpoints and
previously validated measures of exposure). Reproducibility will be assessed by making
repeated measurements in the same subjects on different occasions. Sensitivity to change will
be assessed by comparing values before and after changing smoking habit. Finally, the
validity of the biomarkers will be assessed by comparing them to previous measures of smoke
exposure (CO, NNAL and NNAL-glc) and to clinically defined endpoints: symptoms, the St.
George's Respiratory Questionnaire and post bronchodilator lung function. With regard to the
latter measures, preliminary data indicate that symptoms can be detected in "asymptomatic"
smokers and that these can change with a harm reduction strategy.