Comparison of Blood Test Data Between Patients With COVID-19 and Influenza: a Retrospective Cross-sectional Survey in a Japanese University Hospital

Background: Characteristics features, including blood test data, of COVID-19 compared to those of influenza have not been defined.Purpose: We aimed to compare clinical parameters, including blood test data, between COVID-19 and influenza.Methods: This retrospective cross-sectional survey was conducted at Juntendo University Nerima Hospital, Tokyo, Japan. We recruited patients diagnosed with COVID-19 between January 1 and December 31, 2020, and all patients underwent blood tests. For comparison, we recruited patients diagnosed with influenza. The number of patients with influenza and those with COVID-19 was the same. All patients with influenza underwent blood tests and the period was dated back from December 31, 2020 until the period that was the same number of COVID-19.Results: During the study period, 228 patients (male:female, 123 [54.0%]:105 [46.0%], age [mean±standard deviation], 54.68±18.98 years) were diagnosed with COVID-19. We recruited the same number of influenza patients (228 patients; male:female, 129 [56.6%]:99 [43.4%], age [mean±standard deviation], 69.6±21.25). Age 15–70 years (vs. 71 years), difficulty in breathing, malaise, and percentage of lymphocytes >20% were significantly more frequent in COVID-19. However, nausea, body temperature >38.1°C, and white blood cell count >9000/μL were more frequent in influenza.Conclusion: Our results are useful for differentiating COVID-19 from influenza.