This study aims to describe the characteristics of hospitalised COVID-19 patients in a tertiary care hospital close to an international airport in Japan and to compare these characteristics among different waves during the pandemic.

Retrospective observational study.

Tertiary care centre in Japan.

All patients diagnosed with COVID-19 who were hospitalised between January 2020 and April 2022 were included.

Clinical characteristics, characteristics of admission, treatments and outcomes were investigated and compared among six pandemic waves.

A total of 827 patients were included. The median age was 58.0 years. More than half of the patients (58.3%) had at least one comorbidity. The majority of patients (89.0%) were domestically infected patients admitted under the Infectious Diseases Law, while the remaining patients (11.0%) were those diagnosed during airport quarantine and admitted under the Quarantine Act. Hospital-acquired COVID-19 infection occurred in 7.0% of cases, and mainly during the sixth wave. Overall, some form of oxygen therapy, high-flow oxygen devices, invasive mechanical ventilation (IMV) and extracorporeal membrane oxygenation was provided in 46.3%, 10.4%, 4.5% and 1.5% of cases, respectively. Only 1.8% of patients were treated in the intensive care unit (ICU), and 59.5% of patients on IMV were managed in the non-ICU ward. The in-hospital mortality rate was 5.8%. Median age, percentages of some comorbidities, vaccination coverage, medications for COVID-19, types of supportive care and ICU admissions differed significantly among waves.

This study suggests that patient characteristics, vaccination coverage, standard of treatment and severity of illness changed across waves during the COVID-19 pandemic. Intensive care delivery in non-ICU wards was unavoidable due to limited ICU capacity, which may be a key consideration when preparing for future pandemics.

To evaluate the time-dependent predictive performance of inflammatory markers for 30-day all-cause mortality in patients with suspected infection.

Retrospective cohort study.

The ambulatory care division of the department of general medicine or the emergency department of a single acute care hospital in Japan, from April 2015 to March 2017.

The participants were 977 consecutive adult patients with suspected infection defined as those who underwent at least two sets of blood culture.

The primary outcome, ascertained from electronic medical records, was 30-day all-cause mortality. The predictive performance of three inflammatory markers (C-reactive protein (CRP), neutrophil-to-lymphocyte ratio and red cell distribution width (RDW)) was assessed across four time intervals from symptom onset to hospital presentation: ≤6, >6 to ≤24, >24 to ≤72, and >72 hours.

Time from symptom onset to hospital presentation influenced the predictive performance of inflammatory markers for 30-day all-cause mortality, and CRP ≥15 mg/dL was the most useful for identifying patients at higher risk of mortality within 6 hours (positive likelihood ratio (LR+) 7.7); however, this association weakened over time (LR+ 1.3 at >72 hours). Conversely, RDW ≥16% became more informative later in the course (LR+ 4.1 at >72 hours). For identifying patients at lower risk of 30-day all-cause mortality, CRP

These findings suggest the potential utility of CRP for ruling in high-risk patients within 6 hours from symptom onset, and of RDW for both ruling in and ruling out patients after 72 hours, thereby suggesting that time-dependent variations are important when interpreting inflammatory markers in emergency care settings. However, caution is needed when interpreting these findings because of the retrospective design of this study and potential selection bias.