Novel Breath Test Might Distinguish Fibrotic Lung Conditions

Phoenix -- Researchers unveiled a novel breath test that may help differentiate between idiopathic pulmonary fibrosis (IPF) and fibrotic hypersensitivity pneumonitis, potentially paving the way for noninvasive diagnosis, according to a presentation at the CHEST meeting organized by the American College of Chest Physicians.

The exhaled breath condensate test detected sphingolipids, specifically sphingomyelin C24:0, which accurately predicted fibrotic hypersensitivity pneumonitis in 80% of patients and IPF in 85.7% of cases. This resulted in an area under the receiver operating curve of 0.897. A blood test for plasma dihydrosphingosine demonstrated modest predictive value, with an area under the receiver operating curve of 0.737, and did not substantially enhance the breath test's performance (combined AUC 0.906).

Dr. Jon Mullholand, from Virginia Commonwealth University in Richmond, explained that distinguishing between IPF and fibrotic hypersensitivity pneumonitis is challenging due to their similar clinical presentations, imaging features, and pathologic slides. Accurate diagnosis is crucial as incorrect treatment can negatively impact outcomes and mortality.

The researchers found that sphingolipid species in exhaled breath condensate alone served as the most potent predictor among the noninvasive samples tested. However, these tests are not widely available or accepted by many U.S. laboratories, with exhaled breath condensate being the more accessible of the two. The testing process involves collecting a breath sample in a tube similar to an inhaler, which is then processed in a refrigerator to condense the sample for examination.

Exhaled breath condensate is obtained through a tube similar to an inhaler, where the patient's breath is condensed into a sample that can be analyzed. Despite its potential, research on exhaled breath condensate has waned in recent years, primarily due to practical challenges, such as the assay's volatility and the difficulty in conducting it. The entire procedure takes between 15 and 20 minutes, which can be burdensome for patients with compromised lung function.

Sphingolipids, which play a role in inflammation and fibrosis, have been identified as altered in IPF. Exhaled breath condensate provides insights into the local lung environment, as opposed to the more generalized information obtained from blood samples. In the study, blood samples revealed more changes in IPF, suggesting that it may be a more systemic disease compared to fibrotic hypersensitivity pneumonitis.

Conversely, breath condensate from IPF patients was remarkably similar to that of healthy controls, while breath from fibrotic hypersensitivity pneumonitis patients exhibited significant upregulation, indicating a more localized pulmonary inflammatory state.

The study involved 101 participants, comprising 28 healthy controls, 33 IPF patients, and 40 fibrotic hypersensitivity pneumonitis patients. Among these, 10, 21, and 18 individuals provided exhaled breath condensate, blood samples, and both, respectively. The researchers are optimistic that these findings could lead to further validation studies and potential clinical application, as exhaled breath condensate is cheap, noninvasive, and easy to collect.