D2.391 - Assessment of Small Airway Dysfunction by Impulse Oscillometry in Patients with CVID and Selective IgA Deficiency

Impulse oscillometry (IOS) is a pulmonary function test that evaluates the respiratory system based on resistance principles and provides information about airway function, lung parenchyma, and chest wall elasticity, while requiring minimal patient cooperation. Because IOS requires minimal cooperation and provides insight into airway heterogeneity, it has clinical applications beyond conventional pulmonary function testing (PFT) .

In our study, patients with common variable immunodeficiency (CVID), selective IgA deficiency, and healthy individuals were compared in terms of small airway dysfunction (SAD) using IOS. Thus, the level of SAD in patients with CVID and selective IgA deficiency was assessed in comparison with the normal population.

Twenty-one CVID patients receiving immunoglobulin replacement therapy, nineteen treatment-naïve patients with selective IgA deficiency, and twenty healthy volunteers without structural or chronic lung disease, who were non-smokers and had normal BMI, were evaluated using IOS and standard PFTs. An R5–R20 value greater than 0.07 was considered positive for SAD. In PFT, an FEV1/FVC ratio <80% was interpreted as indicative of obstruction.

Patients with selective IgA deficiency had significantly higher R5–R20 values compared with both CVID patients and healthy controls (p=0.028). In contrast, airflow obstruction was significantly more frequent in patients with CVID than in the other two groups (p=0.015).

To our knowledge, this is the first study evaluating SAD in patients with CVID and selective IgA deficiency. As SAD was more frequently observed in patients with selective IgA deficiency, close monitoring for small airway disease should be considered in this group, even when PFT results are within normal limits.