Can laboratory evaluation differentiate between coronavirus disease-2019, influenza, and respiratory syncytial virus infections? A retrospective cohort study

Aim To identify clinical and laboratory parameters that can assist in the differential diagnosis of coronavirus disease 2019 (COVID-19), influenza, and respiratory syncytial virus (RSV) infections. Methods In this retrospective cohort study, we obtained basic demographics and laboratory data from all 685 hospitalized patients confirmed with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza virus, or RSV from 2018 to 2020. A multiple logistic regression was employed to investigate the relationship between COVID-19 and laboratory parameters. Results SARS-CoV-2 patients were significantly younger than RSV (P= 0.001) and influenza virus (P= 0.022) patients. SARS-CoV-2 patients also displayed a significant male predominance over influenza virus patients (P= 0.047). They also had significantly lower white blood cell count (median 6.3 × 10⁶ cells/μ) compared with influenza virus (P< 0.001) and RSV (P= 0.001) patients. Differences were also observed in other laboratory values but were insignificant in a multivariate analysis. Conclusions Male sex, younger age, and low white blood cell count can assist in the diagnosis of COVID-19 over other viral infections. However, the differences between the groups were not substantial enough and would probably not suffice to distinguish between the viral illnesses in the emergency department.