Seda Yayla1 2Department of Chest Diseases, Dr Suat Seren Chest Diseases and Thoracic Surgery Research and Training Hospital, İzmir, Türkiye; Department of Chest Diseases, University of Health Sciences Turkey Medical Faculty, İzmir Faculty of Medicine, İzmir, Türkiye
3Department of Pulmonary Diseases, University of Health Sciences, Ankara Atatürk Sanatoryum Chest Diseases and Surgery Training and Research Hospital, Ankara, Türkiye
Abstract
Background and Aim: Eosinophilia, defined by an absolute eosinophil count (AEC) ≥500 cells/L, is a common finding associated with various conditions, including mycobacterial infections, and can rarely be induced by standard anti-tuberculosis (TB) drugs like isoniazid, ethambutol, and rifampin. While in vitro studies suggest that eosinophil products like eosinophil peroxidase possess mycobactericidal activity, the clinical impact of eosinophilia on TB outcomes is unknown. This study aimed to analyze the association between eosinophilia development during treatment and the duration of therapy in a retrospective cohort of patients newly diagnosed with drug-sensitive pulmonary TB.
Methods: This was a retrospective cohort study conducted at a tertiary center. A total of 6,045 drug-sensitive pulmonary TB patients treated between 2017 and 2022 were screened. Patients were excluded for conditions that could confound eosinophilia or treatment duration, including allergic diseases, drug-resistant TB, severe comorbidities, and an AEC ≥1500 cells/μL. The final cohort included 121 contemporary non-eosinophilic controls (Group 1) and 119 patients who developed eosinophilia with no identifiable cause (Group 2).
Results: The median age was comparable between Group 1 (43 years, range: 18–82) and Group 2 (45 years, range: 18–84; p=0.485). A statistically significant difference was found in the duration of anti-TB treatment (p=0.013). The median treatment duration for the control group (Group 1) was 7 months (range: 6–9 months), while the median duration for the eosinophilia group (Group 2) was 6 months (range: 6–9 months). Logistic regression analysis confirmed that eosinophilia was significantly associated with treatment duration (OR: 2.06, (95% CI: 1.14–3.71; p=0.017).
Conclusion: The development of eosinophilia during treatment in drug-sensitive pulmonary TB is associated with a significantly shorter treatment duration. Conversely, the absence of eosinophilia is an independent risk factor for prolonged therapy. These findings suggest that eosinophils may contribute to a more effective host immune response against Mycobacterium tuberculosis, serving as a potential positive prognostic indicator in clinical practice.
