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Researchers reported that a sphingolipid measured in exhaled breath condensate distinguished idiopathic pulmonary fibrosis from fibrotic hypersensitivity pneumonitis in a small study. The results are promising but preliminary; external validation and practical testing methods are needed before the approach could be used in routine care.
A breath-condensate test measuring the lipid sphingomyelin C24:0 distinguished idiopathic pulmonary fibrosis (IPF) from fibrotic hypersensitivity pneumonitis with promising accuracy in a study presented October 20 at the CHEST meeting in Phoenix. The result points to a possible noninvasive aid for separating diseases that can look similar, but the findings have not yet been externally validated and the test is not established for routine clinical use.
The study included 101 people who provided blood samples: 28 healthy controls, 33 patients with IPF and 40 with fibrotic hypersensitivity pneumonitis. Breath-condensate samples were available from a smaller group: 10 controls, 21 IPF patients and 18 patients with fibrotic hypersensitivity pneumonitis. Jon Mullholand, MD, of Virginia Commonwealth University, reported the findings at the meeting hosted by the American College of Chest Physicians.
Sphingomyelin C24:0 in breath condensate correctly predicted fibrotic hypersensitivity pneumonitis in 80% of cases and IPF in 85.7%. Its area under the receiver operating characteristic curve was 0.897, a measure of how well a test separates groups. A blood marker, plasma dihydrosphingosine, had a lower AUC of 0.737 on its own. Adding it to the breath-test model raised the AUC to 0.906, a limited change from the breath marker alone.
The researchers described the breath marker as the strongest predictor they had seen using noninvasive sampling, but that assessment comes from this study and needs confirmation. The reported performance does not establish how the test would work across a broader patient population, or whether using it would improve diagnosis or treatment decisions.
A Potential Aid in Disease Classification
IPF and fibrotic hypersensitivity pneumonitis can share clinical symptoms, imaging patterns and even pathology findings, particularly in advanced disease, Mullholand said. Yet the conditions differ in management and prognosis. A test that helps clinicians tell them apart could support diagnostic decisions where existing evidence is difficult to interpret.
The potential value is not that a breath test would replace clinical assessment. Rather, it could add another source of evidence without requiring an invasive sample. Mullholand warned that choosing the wrong treatment in either direction can affect outcomes and potentially mortality. That is a reason to investigate better diagnostic tools, not evidence that this test has already changed patient care.
The study also raises a research question about whether the measured lipids reflect disease processes in the lungs. If validated, the signal might help researchers examine how sphingolipids relate to inflammation and fibrosis. The study does not show that these lipids cause either condition.
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Why Breath Samples May Differ
Sphingolipids are involved in processes related to inflammation and fibrosis, and previous research has reported altered sphingolipids in IPF. Breath condensate may reflect the local lung environment, while blood can provide a broader, systemic picture, Mullholand said. In this study, he described breath-condensate results from IPF patients as similar to controls, while levels in fibrotic hypersensitivity pneumonitis were more elevated. Those patterns are observations from the study, not a settled explanation of the diseases.
Collecting exhaled breath condensate involves breathing into a tube-like device. A refrigerant condenses moisture from the breath into a sample for analysis. Mullholand said collection can take 15 to 20 minutes and may be difficult for people with severe lung disease. He also described the assay as technically challenging and said the relevant tests are not commonly available: plasma sphingolipid testing is not a common assay, and many U.S. laboratories do not accept breath-condensate samples for analysis.
The report therefore describes an early diagnostic study, not a ready-to-use test. The sample sizes for breath analysis were particularly small, and an accuracy estimate from one research cohort cannot by itself establish performance in other clinics or patient groups.
“There’s a diagnostic challenge when we’re trying to differentiate these [two conditions] at end-stage disease, as they can have overlapping clinical presentations as well as imaging features, even pathologic slides.”
— Jon Mullholand, MD, of Virginia Commonwealth University, speaking at the CHEST meeting
Validation and Testing Gaps
The findings remain preliminary. The breath-test analysis involved 49 participants across the three groups, and the report does not establish performance in an independent cohort. Mullholand said external validation is needed before the results can support wider clinical use. It is also unclear whether the reported accuracy would hold in patients whose diagnosis is uncertain in ordinary clinical settings.
The study does not show whether the test changes treatment choices or improves health outcomes. Further details about thresholds, reproducibility between laboratories and how the test might fit alongside imaging, pathology and other clinical information are not established in the source report. Availability is another obstacle: the assay is not routinely offered by many laboratories, and breath collection can be burdensome for people with severe lung disease.
External Studies Before Clinical Use
The next stated step is external validation in a separate group of patients. Researchers would need to confirm the breath marker’s performance, assess whether laboratories can produce consistent results and determine how useful it is alongside current diagnostic methods. The study report does not give a timeline for those studies or say when a clinical assay might become available.
Mullholand also said the lipid findings could prompt work on the biological pathways involved in fibrosis. Further research would need to determine whether sphingolipids contribute to disease processes or are a consequence of them. Until validation and clinical utility are demonstrated, the breath test should be viewed as a research finding rather than a recommended diagnostic test.
Key Questions
What did the breath test measure?
It measured sphingomyelin C24:0, a sphingolipid, in exhaled breath condensate—the collected moisture from a person’s breath.
Which conditions did the study compare?
The researchers studied idiopathic pulmonary fibrosis and fibrotic hypersensitivity pneumonitis, along with healthy controls.
How accurate was the test in the study?
The marker correctly predicted fibrotic hypersensitivity pneumonitis in 80% of cases and IPF in 85.7%. These results came from a small study and have not yet been confirmed in an external validation study.
Can patients get this test now?
The report says breath-condensate analysis is not accepted by many U.S. laboratories, and the plasma sphingolipid test is not a common assay. The findings do not establish the breath test as available or recommended for routine care.
What needs to happen before the test is used in clinics?
Researchers need to confirm its performance in an independent patient group and establish reliable testing methods. They also need to show how the result could inform diagnosis and whether it adds useful information to existing clinical assessments.
Source: rss
