Evaluating the relationship between high-resolution computed tomography findings and their extent in eosinophilic lung diseases with peripheral blood eosinophil level

Introduction
Eosinophilic lung diseases are a group of pulmonary disorders associated with peripheral or tissue eosinophilia. They can be classified into primary (idiopathic) and secondary groups based on their aetiology. On the other hand, blood eosinophilia is a common clinical problem with various causes. In many cases the lung infiltrations in patients with peripheral eosinophilia are non-eosinophilic. Herein, we aim to assess the relationship between blood eosinophilia and abnormal high-resolution computed tomography (HRCT) features and their extent in idiopathic chronic eosinophilic pneumonia (ICEP) (the most common form of idiopathic eosinophilic lung disease). This can help in differentiating eosinophilic from non-eosinophilic lung infiltrations in patients with blood eosinophilia.

Material and methods
In this descriptive-correlational study, all patients with proven ICEP, who were referred to Masih Daneshvari Hospital, Tehran, Iran from 2012 to 2019, were included. The ICEP diagnosis was based on lung infiltrations on imaging, in addition to increased numbers of eosinophils in bronchoalveolar lavage fluid, blood or lung biopsy samples, and rapid response to corticosteroids. Patients with known aetiologies for eosinophilic lung diseases were excluded. The HRCT findings and their extent in each patient were compared with the blood eosinophil level.

Results
Positive correlation was found only between blood eosinophil level and frequency and extent of consolidation, and with frequency of lymphadenopathy.

Conclusions
HRCT can help to differentiate eosinophilic from non-eosinophilic lung infiltrations in patients with blood eosinophilia by comparing the extent of consolidation with the blood eosinophil level.