Total immunoglobulin E levels in induced sputum reflect asthma control status.

Background: Most patients with severe asthma are sensitized to at least one allergen. Whether local immunoglobulin E (IgE) in induced sputum reflects asthma control status has not been investigated.

Methods: Patients with asthma were classified as well controlled, partly controlled, and uncontrolled asthma (UCA) according to Global Initiative for Asthma 2022 guidelines. Lung function and fractional exhaled nitric oxide (FeNO) were evaluated. Induced sputum was collected and total IgE and Phadiatop (IgE to common inhalant allergens) measurements were performed. General clinical characteristics and pulmonary inflammation indicators were analyzed between the three groups of asthmatic patients. Univariate and multifactor ordinal logistic regression were used to model the relationship between pulmonary inflammation indicators and asthma control status. The ability of sputum total IgE in identifying different levels of asthma control was assessed by receiver operating characteristic curve (ROC).

Results: Patients with UCA had worse lung function and airway inflammation as indicated by lower levels of forced expiratory volume in 1s (FEV1)%pred, FEV1/FVC, MEF75%pred, MEF50%pred and MEF25%pred, and higher levels of FeNO and sputum eosinophil% compared with the WCA group. In addition, higher levels of total sputum IgE and Phadiatop were found in patients with UCA than in patients with WCA and PCA. Univariate and multifactor ordinal logistic regression analysis indicated that sputum total IgE was the unique significant risk factor for poor asthma control (adjusted odds ratio = 6.25; 95% CI, 1.07-36.55; p < 0.05) among pulmonary inflammation indicators including different indices of pulmonary function test, sputum IgE and FeNO. Sputum total IgE levels showed a significant correlation with asthma control scores (r = 0.53, p < 0.001). Moreover, ROC analysis showed that the predictive value of sputum total IgE for patients with UCA was 0.82 (95% CI, 0.74-0.9).

Conclusion: Sputum total IgE reflects levels of asthma control, and can be used as an indicator of UCA.