Real-time exhaled breath analysis using secondary electrospray ionization-mass spectrometry has validated previous findings of elevated lung tissue amino acid levels in idiopathic pulmonary fibrosis (IPF), claims a new study, suggesting that online breath analysis can be a practical tool for rapid screening for IPF.

Significantly increased levels of proline, 4-hydroxyproline, alanine, valine, leucine/isoleucine and allysine were found in breath of IPF patients. However, pyroglutamic acid and phenylalanine did not show significant differences.

“This coincides with the amino acid's abundance in pulmonary tissue indicating that our observations reflect progressing fibrosis,” the investigators said.

Amino acid levels were also correlated across patients, providing evidence of a common underlying pathway. Furthermore, a cross-validated area under the curve of 0.86 was achieved. This suggested that elevated amino acid levels in exhaled breath have the potential to be used as biomarkers for IPF.

According to the investigators, IPF diagnosis is complicated and its pathogenesis is poorly understood, with recent findings showing increased levels of proline and other amino acids in lung tissue of IPF patients. They believe that these could have diagnostic significance.

“Following these findings, we hypothesized that such altered metabolic profiles would be mirrored in exhaled breath and could therefore be captured noninvasively in real time,” they said.

The investigators sought to validate these results with the use of real-time exhaled breath analysis by secondary electrospray ionization-mass spectrometry, which offers a noninvasive, painless and fast insight into the metabolism. They conducted breath analysis in a matched 1:1 case–control study involving 21 patients with IPF and 21 control participants.