Introduction/Aim COPD patients with peripheral eosinophilia may have increased frequency of COPD exacerbations, respond better to oral corticosteroids and reduced mortality. Peripheral eosinophilia in COPD patients (eosinophil count of ≥ 2% of white blood cell count) has a prevalence in the range of 37‐45%. To our knowledge, there is little epidemiological data of Australian COPD patients concerning peripheral eosinophilia, its prevalence and its association with rehospitalisation rates, steroid responsive disease and mortality rates. With this literature gap in mind, records of patients presenting with COPD exacerbations were audited retrospectively to determine the prevalence of peripheral eosinophilia in an Australian population.

Methods Consecutive patients with spirometry confirmed COPD admitted to our institution with a COPD exacerbation during the period of July 2016 – December 2016 were considered for the study. These patients' records were subsequently followed up until June 2017. The variables recorded were white blood cell count, absolute and relative eosinophil count, readmission rate, decompensated type 2 respiratory failure rate, non‐invasive ventilation initiation rate, intensive care admission rate and mortality rate.

Results 240 patients were included for analysis and of these 37% had peripheral eosinophilia. Using Pearson's coefficient, there appeared to be a statistically significant correlation between increasing peripheral eosinophil count and increased number of readmissions (R=0.175, p=0.007) but not with decompensated type 2 respiratory failure, non‐invasive ventilation initiation rate, intensive care admission rate or mortality rate. Two‐sample t‐Test for equal means when comparing those with peripheral eosinophilia ≥ 2% and those without was also in keeping with a statistically significant difference in readmission rates (t=‐2.367, p=0.019).

Conclusion Prevalence of peripheral eosinophilia in Gold Coast patients was similar to overseas cohorts. In congruence with findings in previous overseas studies, Gold Coast patients with eosinophilia were prone to readmission but not increased type 2 respiratory failure, non‐invasive ventilation, intensive care admission or mortality. As such peripheral eosinophilia can be used in Australian COPD patient cohorts to predict rehospitalisation rate. Future studies should look to prospectively evaluate the effect inhaled corticosteroids have on readmission rates in patients with peripheral eosinophilia.