Asthma that looks mild on paper but feels severe in life
Published online July 17, 2025
Asthma is a common chronic lung disease caused by persistent airway inflammation. The most recognized and well-studied type is called type-2 (T2) inflammation. Although there is no single agreed set of markers and their cut-off values for identifying T2 inflammation, three are commonly used: blood eosinophil count (BEC), fractional exhaled nitric oxide (FeNO), and whether asthma is clearly linked to allergies. Because the type of inflammation shapes both how asthma presents and how it responds to treatment, it is important in everyday clinical care to assess patients in relation to these T2 inflammation markers.
The West Sweden Asthma Study (WSAS) is a population-based study that follows adults both with and without asthma. Participants answered detailed questionnaires and took part in several health checks, including blood tests, breathing tests, and skin prick tests. In a recent article published in The Journal of Allergy and Clinical Immunology: In Practice, Ercan et al. grouped people with asthma into two categories - those with low levels of T2 inflammation markers and those with high levels - and compared their health characteristics. The authors used the GINA 2024 report to classify participants. People were considered to have “asthma with high T2 markers” if at least one of the following signs was present: higher levels of certain blood cells (eosinophils), higher levels of nitric oxide in the breath, or asthma clearly linked to allergies. Those without any of these signs were grouped as having “asthma with low T2 markers.” The only people excluded were those missing test results for these measures. To better reflect real life, no other restrictions were applied, so that people were not excluded because of smoking, other health conditions, medicines, weight, age, or asthma severity.
A total of 896 people participated in the study. Among them, 1 in 7 had asthma with low T2 markers (128 people, 14.3%). This group included more females and tended to develop asthma later in life. Rates of obesity and smoking were similar between groups. People with low T2 markers generally had better lung function on breathing tests, but they were more likely to need emergency care and to miss work or daily activities for at least two days in the past year because of worsening asthma symptoms. In short, even though lung function looked better, people with low T2 markers experienced a heavier burden of disease. Therefore, they need special attention in asthma care.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.
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