Absolute Eosinophil Count as a marker to differentiate COVID-19 from other short febrile illness

Purpose: Peripheral blood routine examination results are often abnormal in Covid-19. This study aimed to determine whether absolute eosinophil count can be used as a marker to differentiate covid-19 from other short febrile illness Materials and Methods: This was a single-center retrospective descriptive study which studied 1000 laboratory confirmed Covid-19 patients and 300 patients with non-Covid short febrile illness. The peripheral blood routine examination results and relevant demographic parameterson the first day of hospital visit for both groups; and the clinical disease severity category assigned to each patient in the Covid-19 group were obtained from the hospital electronic medical records and analysed at the end of the study using appropriate statistical tools. Results: The median AEC was 55 cells/mm3 (13.2-140.4) and 167.57cells/mm3 (83.6-247.4) in the Covid and non-Covid groups respectively (p < 0.001). The median NLR was 2.6 (1.5-5.3) and 2.7 (1.9-4.2) in the Covid and non-Covid groups respectively (p=0.689). Upon comparing mild, moderate and severe clinical disease severity, median AEC was lowest and median NLR was highest in the severe category (p< 0.001) Conclusion: A low AEC may help differentiate Covid-19 infection from other short febrile illness when used in conjunction with clinico-radiological features. An initial low AEC and high NLR can predict increased clinical disease severity.