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Researchers reported that sphingomyelin C24:0 in exhaled breath condensate distinguished idiopathic pulmonary fibrosis from fibrotic hypersensitivity pneumonitis in a study presented at the CHEST meeting. The result is promising but preliminary: breath samples came from only 49 patients, and the test needs external validation before its accuracy or clinical role is established.
Researchers reported that a lipid found in exhaled breath condensate may help distinguish idiopathic pulmonary fibrosis (IPF) from fibrotic hypersensitivity pneumonitis, two conditions that can look similar in advanced disease. In the study presented at the CHEST meeting in Phoenix, sphingomyelin C24:0 classified the conditions with reported accuracy of 80% and 85.7%, respectively; the findings remain preliminary and require external validation.
The study assessed 101 participants: 28 healthy controls, 33 people with IPF and 40 with fibrotic hypersensitivity pneumonitis. Breath condensate was available for a smaller subset: 10 controls, 21 people with IPF and 18 with fibrotic hypersensitivity pneumonitis. The researchers examined sphingolipids, a group of fats involved in processes including inflammation and fibrosis.
Sphingomyelin C24:0 in breath condensate had an area under the receiver operating characteristic curve (AUC) of 0.897. The report said it correctly predicted fibrotic hypersensitivity pneumonitis in 80% of cases and IPF in 85.7%. A separate blood measure, plasma dihydrosphingosine, had an AUC of 0.737. Adding it to the breath test raised the combined AUC to 0.906, a small increase in the reported measure.
The results were presented by Jon Mullholand, MD, of Virginia Commonwealth University, at the meeting hosted by the American College of Chest Physicians. The figures describe performance in this study; they do not establish how the test would perform in routine care or in a new patient group.
A Potential Aid to Lung Diagnosis
IPF and fibrotic hypersensitivity pneumonitis can have overlapping symptoms, imaging findings and pathology, particularly in advanced disease, Mullholand said. Distinguishing them matters because their management and prognosis differ. A test that helps clarify the diagnosis could inform clinical decisions, although this study does not show that using the breath test improves treatment choices or patient outcomes.
The proposed sample is collected by condensing exhaled breath, potentially offering a noninvasive alternative to more involved diagnostic approaches. But promising accuracy in a small research sample is not the same as a validated clinical test. The findings support further investigation, not immediate adoption as a standard diagnostic method.
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Why Breath Samples May Help
Mullholand said the two diseases can be difficult to separate at end stage even when clinicians consider clinical presentation, imaging and pathology. He described breath condensate as a way to examine the local lung environment, while blood may reflect broader changes across the body. In the study, breath-condensate patterns differed more clearly in fibrotic hypersensitivity pneumonitis, while blood samples showed more changes in IPF.
Collecting condensate involves breathing into a tube-like device; a refrigerant cools the breath so a sample can be gathered for testing. The procedure can take 15 to 20 minutes, and Mullholand said it may be difficult for people with severe lung disease. He also described the assay as technically challenging and said testing is not commonly available: plasma sphingolipid testing is not a common assay, and many U.S. laboratories do not accept breath condensate for analysis.
“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
Accuracy Needs Outside Testing
The reported performance comes from a single study with 39 breath samples from the two patient groups, alongside 10 control samples. The source report does not provide an external validation cohort or establish how the test performs across different clinics, disease stages or patient populations. The reported percentages and AUC therefore should not be treated as confirmed accuracy in general practice.
It is also unclear how a breath test would fit alongside existing diagnostic assessments, what threshold clinicians would use, or whether the result would change care. The study does not establish that sphingomyelin C24:0 causes either disease, or whether its presence reflects a disease mechanism or a consequence of illness. Practical barriers include sample collection time, assay variability and limited laboratory availability.
External Validation Is the Next Step
Mullholand said the findings need an external validation study before the approach can be considered for clinical use. Such research would need to test the marker in a separate group of patients and clarify how consistently the sample can be collected and analyzed. The report did not give a timeline for that work.
Researchers may also investigate whether the sphingolipid pattern provides clues to disease biology, rather than serving only as a classifier. For now, the study is a meeting report and the test is not described as a commonly available or accepted clinical assay. Patients should continue to rely on their clinicians’ established diagnostic assessment rather than use this finding as a basis for changing care.
Key Questions
What did the study find?
Researchers reported that sphingomyelin C24:0 in exhaled breath condensate distinguished IPF from fibrotic hypersensitivity pneumonitis in their study. Reported classification figures were 80% for the latter condition and 85.7% for IPF.
Is this breath test available for patients now?
The report says breath-condensate testing is not accepted for analysis by many U.S. laboratories, and plasma sphingolipid testing is not a common assay. The study does not establish this as a routine clinical test.
How many people provided breath samples?
Forty-nine people provided breath condensate: 10 healthy controls, 21 people with IPF and 18 with fibrotic hypersensitivity pneumonitis. The larger study included 101 participants who provided blood samples.
What needs to happen before the test could be used in care?
The findings need external validation in a separate patient group, along with more evidence on the test’s reliability and practical use. The study did not show that the test improves treatment decisions or outcomes.
Source: rss
