Using this cut-off value in the Kaplan-Meier analysis, COVID-19 patients with highly elevated HE4 levels had a significantly higher risk for 30-day mortality compared to those with lower HE4 concentrations (with a death ratio of 71% vs. 19%, respectively, Log rank P < 0.0001) (Fig. 4). The gene discussed is WFDC2; the disease is COVID-19.