Eosinophil counts and LDH levels tend to return to normal range over time in non-severe patients
We further analyzed the eosinophil counts and LDH levels in non-severe and severe COVID-19 patients with chronic bronchitis, COPD, and asthma, respectively. We found that there was a significant difference in eosinophil counts and LDH levels between severe and non-severe patients with chronic bronchitis and COPD whereas not in patients with asthma (Figure 1). To observe the dynamic changes of eosinophil counts and LDH levels over time, we collected the eosinophil counts and LDH levels on the 5th, 10th, 15th, 20th, 25th, and 30th day after admission. We found that eosinophil counts increased over time both in severe and non-severe patients. Meanwhile, LDH decreased over time (Figure 2). Severe patients showed a slower recovery rate than non-severe patients, especially eosinophil counts. Of note, both eosinophil counts and LDH levels recovered more slowly in severe patients with COPD than those in severe patients with chronic bronchitis and asthma. Our data suggest that, as the disease improved, eosinophil counts and LDH levels tend to return to normal range both in severe and non-severe patients, indicating a good therapeutic effect of patients with chronic airway diseases in COVID-19 treatment.
We further performed multivariate analysis for mortality in COVID-19 patients with chronic airway inflammation using the above four variables and found that eosinophil counts < 0.02×10⁹/L (odds ratio per 1 unit increase, 18.000 [95% CI 1.929-167.986], p = 0.011) was the only independent risk factor for mortality (Supplementary Table 1). Moreover, Kaplan-Meier survival curves indicated that COVID-19 patients with eosinopenia or elevated LDH had worse survival probability (p < 0.05) (Supplementary Figure 1). This suggests that eosinopenia and elevated LDH are also potential predictors for the mortality of COVID-19 patients with underlying chronic airway diseases.