Many patients with severe uncontrolled asthma may have undetected small airways dysfunction (SAD) even when standard lung function tests appear normal. That’s according to the paper, “Oscillometry Defined Small Airways Dysfunction Patients With Severe Uncontrolled Asthma and Preserved Spirometry,” recently published in the journal, Respiratory Medicine.
SAD is increasingly recognized as an important and treatable feature of asthma, Scottish researchers noted in their study, yet it is often overlooked in routine clinical practice. Traditionally, physicians have relied on spirometry to assess airway function, they said, but commonly used spirometric measures can be limited because they depend heavily on patient effort and lung volume during testing. The researchers said this discovery could open the door to using oscillometry, a more sensitive diagnostic technique.
To investigate the prevalence of SAD, researchers reviewed 67 biologic-naive patients with severe uncontrolled asthma who were preparing to begin biologic therapy at a center in Tayside, Scotland. The team compared spirometry results with measurements obtained through oscillometry, an effort-independent technique that assesses airway resistance and can provide a more detailed picture of small airway function.
The findings revealed that SAD was present in 63% of patients overall. Among the 31 patients whose spirometry results appeared normal (showing preserved FEV1 and FEV1/FVC ratios), only 6% demonstrated abnormalities using a traditional spirometry marker of SAD. By contrast, 29% showed abnormalities when assessed with oscillometry, suggesting that standard testing may miss a substantial proportion of patients with underlying airway disease.
Researchers also found that patients with evidence of SAD reported significantly worse symptom control than those without the condition. According to the study’s authors, individuals with SAD had higher Asthma Control Questionnaire (ACQ) scores, indicating a greater symptom burden, even though markers of type 2 inflammation and annual exacerbation rates did not differ significantly between groups.
Investigators noted that the study builds on previous research, including the ATLANTIS study, which demonstrated that the prevalence of SAD increases with asthma severity. The current findings, they noted, further suggest that oscillometry may be especially valuable for identifying patients whose disease remains hidden despite normal spirometry results.
According to the researchers, the results reinforce the importance of evaluating SAD as a distinct asthma trait that can affect symptom control and quality of life. They emphasized that incorporating oscillometry alongside conventional spirometry could help physicians identify more patients who may benefit from targeted treatment strategies.
