Instrumental drift removal in GC-MS data for breath analysis: the short-term and long-term temporal validation of putative biomarkers for COPD

摘要

Breath analysis holds the promise of a non-invasive technique for the diagnosis of diverse respiratory conditions including chronic obstructive pulmonary disease (COPD) and lung cancer. Breath contains smallmetabolites that may be putative biomarkers of these conditions.However, the discovery of reliable biomarkers is a considerable challenge in the presence of both clinical and instrumental confounding factors.Among the latter, instrumental time drifts are highly relevant, as since question the short and longterm validity of predictive models. In thisworkwe present amethodology to counter instrumental drifts using information from interleaved blanks for a case study of GC-MS data from breath samples.The proposed method includes featurefiltering, and additive, multiplicative andmultivariate drift corrections, the latter being based on component correction. Biomarker discovery was based on genetic algorithms in a filter configurationusing Fisher's ratio computed in the partial least squares-discriminant analysis subspace as a figure ofmerit. Using our protocol,we have been able to find nine peaks that provide a statistically significant area under the ROC curve of 0.75 for COPDdiscrimination. Themethod developed has been successfully validated using blind samples in short-term temporal validation.However, the attempt to use this model for patient screening six months laterwas not successful.This negative result highlights the importance of increasing validation rigorwhen reporting biomarker discovery results.