Differentiating diagnosis of COVID-19 or influenza in patients based on laboratory data during flu season

Both coronaviruses and influenza A viruses (IAVs) are general pathogens which are responsible for the seasonal cold. However, a new coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is pulling the world into the torment of the COVID-19 pandemic [1]. As the SARS-CoV-2 is still circulating in almost every continent with its ability for airborne and asymptomatic transmission [2], it would be very likely that the COVID-19 pandemic will overlap with the influenza epidemic in the coming winter [3]. COVID-19 shares many clinical symptoms with pneumonia caused by IAVs, but its fatality rate is much higher than that of seasonal flu [4]. Therefore, to precisely treat patients with respiratory diseases during the epidemic season, it would be very important that doctors are able to differentiate COVID-19 from seasonal influenza based on laboratory data as early as possible. Currently published clinical and laboratory data on COVID-19 are limited to studies with small sample sizes mostly originating from China. In the study, Ji et al. in Northwestern University reveals significant differences in laboratory parameters between hospitalized COVID-19 and influenza patients in the US, with a sample size of more than 1000 cases [5]. Instead of comparing clinical endpoints to evaluate risks, they compiled and temporally tracked all available laboratory results of the hospitalized patients from the day of presentation to day 14. Compared to influenza patients, the most significant differences over the course of 14 days of hospitalization in COVID-19 patients were faster worsening anemia and leukocytosis, and a more rapid increase in D-dimer, BUN, and ALT. The level of lactate dehydrogenase (LDH) was significantly higher in patients with influenza. However, the most commonly reported laboratory abnormalities in