The Hospital Recovery Scale: A clinically useful endpoint in patients hospitalized with influenza

Background: Currently, no single best primary endpoint exists for measuring the efficacy of treatments in seriously ill patients with respiratory infections, such as influenza, who require hospitalization. The Hospital Recovery Scale is an ordinal endpoint used to evaluate treatment outcomes in clinical studies of hospitalized patients infected with influenza. Methods: To determine whether Hospital Recovery Scale outcomes correspond to those for other clinical endpoints in patients hospitalized due to influenza, data from the phase 3 randomized, double-blind ZORO clinical trial (NCT01231620) were analyzed. Randomized influenza-infected patients were divided into sub-groups of interest based on prespecified baseline and infection-related characteristics, as well as randomized treatment arms (intravenous zanamivir 300 mg or 600 mg, or oral oseltamivir 75 mg). Clinical endpoints relevant to this population were included to analyze differences in outcomes between the subgroups, and cor-respondence of these endpoints and hospital recovery endpoint was evaluated. Results: Data from 488 patients were analyzed. There were strong correlations (rho s > 0.8) between the Hospital Recovery Scale assessed on the day after completion of a 5-day antiviral therapy (Day 6) and both time to hospital discharge and time to intensive care unit discharge, and moderate to strong correlations (0.6 < rho s < 0.8) between the Hospital Recovery Scale on Day 6 and several other relevant clinical endpoints. Conclusions: The Hospital Recovery Scale is applicable as a primary endpoint in trials to evaluate new therapies for severely ill patients hospitalized due to influenza, and may have utility in other severe respiratory illnesses such as COVID-19.