1Department of Family Medicine and Public Health, Sultan Qaboos University Hospital, Muscat, Oman; 2Department of Dermatology, Jewish General Hospital, McGill University, Montreal, Canada *Corresponding Author’s e-mail: a.alkhalili@hotmail.com Re: Elevated Peripheral Blood Eosinophils during Acute Exacerbation of Chronic Obstructive Pulmonary Disease Prevalence and clinical significance Sultan Qaboos University Med J, November 2022, Vol. 22, Iss. 4, pp. 595–596, Epub. 7 Nov 22 Submitted 24 Aug 22 Accepted 15 Sep 22 This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License. https://doi.org/10.18295/squmj.10.2022.060 LETTER TO THE EDITOR Dear Editor, We read with interest, the article by Al Sibani et al. published in the August 2022 issue of SQUMJ.1 on elevated peripheral blood eosinophils (PBE) during acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Patients who have been treated for COPD may develop acute exacerbations and respond to corticosteroids.2 Pulmonary function tests in these patients show that FEV1.0 can be markedly improved in stable conditions after corticosteroid administration.2 In the last several years, we also encountered three COPD patients with increased peripheral eosinophils during acute exacerbations. Two of them were severe COPD patients who required home oxygen therapy. Intravenous corticosteroids resulted in marked improvement in the patient's symptoms and FEV1.0. Therefore, we speculate that some patients who seem to have only COPD might have factors of bronchial asthma. We agree with the authors' view that peripheral eosinophil counts during acute exacerbations should be noted. However, there are some aspects where questions remain. It would be beneficial to know whether it was considered that increased eosinophils suggested that the patients had bronchial asthma. It was unclear if the patients had a history of paroxysmal dyspnoea at night or early in the morning or if there were any changes in EEV1.0 before and after beta-agonist inhalation in pulmonary function tests. For patients who had exacerbation eosinophilia, it was not clear if the peripheral eosinophil counts remained normal in the resting state when steroids were restored to pre-exacerbation levels. Finally, it would be helpful to know whether patients with eosinophilia were considered those with so-called ‘asthma-chronic pulmonary obstructive disease overlap’.3 Shinichiro Okauchi and *Hiroaki Satoh Division of Respiratory Medicine, Mito Medical Center, University of Tsukuba-Mito Kyodo General Hospital, Mito, Japan *Corresponding Author’s e-mail: hirosato@md.tsukuba.ac.jp References 1. Al Sibani M, Al Alawi AM, Al Aghbari J. Elevated Peripheral Blood Eosinophils during Acute Exacerbation of Chronic Obstructive Pulmonary Disease: Prevalence and clinical significance. Sultan Qaboos Univ Med J 2022: 22;339–42. https://doi.org/10.18295/squmj.8.2021.099. 2. Hizawa N. Pharmacogenetics of chronic obstructive pulmonary disease. Pharmacogenomics 2013; 14:1215–25. https://doi.org/10.2217/ pgs.13.107. 3. Cazzola M, Rogliani P, Matera MG. Unmet needs and the future of asthma-chronic pulmonary obstructive disease overlap. Immunol Allergy Clin North Am 2022; 42:691–700. https://doi.org/10.1016/j.iac.2022.04.006. Response from the Authors Dear Reader, Eosinophilic airway inflammation has been an increasingly recognised subtype of COPD and is unrelated to bronchial asthma.1,2 In addition, the Strategy for the Diagnosis, Management and Prevention of Chronic Obstructive Pulmonary Disease proposed by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) has recommended initiating inhaled steroids of patients with stable COPD based on the eosinophils count.3 In regards to our sample, we excluded all patients with a history of bronchial asthma or symptoms suggestive of bronchial asthma;4 also, we have used the GOLD criteria to ascertain COPD diagnosis for all patients in our study.5 https://creativecommons.org/licenses/by-nd/4.0/ https://doi.org/10.18295/squmj.8.2021.099. https://doi.org/10.2217/pgs.13.107. https://doi.org/10.2217/pgs.13.107. https://doi.org/10.1016/j.iac.2022.04.006. Re: Elevated Peripheral Blood Eosinophils during Acute Exacerbation of Chronic Obstructive Pulmonary Disease Prevalence and clinical significance 596 | SQU Medical Journal, November 2022, Volume 22, Issue 4 With steroid therapy, a remarkable reduction in eosinophils count was noted from 0.6 cells × 109/L on admission to 0.2 cells × 109/L on discharge; however, there are no follow-up data on eosinophils counts when patients returned to the pre-exacerbation state. In our study, patients with elevated eosinophilic count had a shorter length of hospital stay but a higher one-year readmission rate. Our findings support the possibility that elevated eosinophils count is a unique entity related to a subtype of COPD rather than a manifestation of overlap between COPD and bronchial asthma, hence eosinophilic count should be used as a surrogate marker to guide steroid use in acute exacerbation of COPD and to guide long-term steroid treatment. *Abdullah M. Al Alawi, Maitha Al Sibani, Jamal Al Aghbari Department of Medicine, Sultan Qaboos University Hospital, Muscat, Oman; Oman Medical Specialty Board, Muscat, Oman *Corresponding Author’s e-mail: dr.abdullahalalawi@gmail.com References 1. Saha S and Brightling CE. Eosinophilic airway inflammation in COPD. Int J Chron Obstruct Pulmon Dis 2006; 1:39–47. https://doi. org/10.2147/copd.2006.1.1.39. 2. Ashdown HF, Smith M, McFadden E, Pavord ID, Butler CC, Bafadhel M. Blood eosinophils to guide inhaled maintenance therapy in a primary care COPD population. ERJ Open Res 2022; 8:00606-2021. https://doi.org/10.1183/23120541.00606-2021. 3. Oliver B, Tonga K, Darley D, Rutting S, Zhang X, Chen H, et al. COPD treatment choices based on blood eosinophils: are we there yet? Breathe (Sheff ) 2019; 15:318–23. https://doi.org/10.1183/20734735.0254-2019. 4. Al Sibani M, Al Alawi A and Al Aghbari J. Elevated Peripheral Blood Eosinophils during Acute Exacerbation of Chronic Obstructive Pulmonary Disease: Prevalence and clinical significance. Sultan Qaboos Univ Med J 2022; 22:339–42. https://doi.org/10.18295/ squmj.8.2021.099. 5. Global Initiative for Chronic Obstructive Lung Disease. 2020 Global Strategy for Prevention, Diagnosis and Management of COPD. From: https://goldcopd.org/gold-reports/ Accessed: Sep 2021. https://doi.org/10.2147/copd.2006.1.1.39. https://doi.org/10.2147/copd.2006.1.1.39. https://doi.org/10.1183/23120541.00606-2021. https://doi.org/10.1183/20734735.0254-2019. https://doi.org/10.18295/squmj.8.2021.099. https://doi.org/10.18295/squmj.8.2021.099.