Comparison of COVID-19 mortality at the first and second wave adjusted for the 4C mortality score

Abstract

Background: Second wave COVID-19 inpatient mortality may have been reduced by dexamethasone, targeted use of high-flow ventilation techniques or non invasive or mechanical ventilation.

Aims and Objectives: To compare mortality of the first and second wave of COVID-19, adjusted for the 4C Mortality Score (4C-MS).

Methods: Consecutive COVID-19 positive patients admitted at the Centre Hospitalier du Valais Romand were followed until discharge or death. A modified 4C-MS (not including Glascow coma scale), extracted from electronic data, was chosen to adjust for the risk of death. Missing data for the 4C-MS were filled in with multiple imputation techniques.

Results: Among 1211 COVID-19 cases in 2020, 73.4% were admitted at the second wave. Mean age was 71.1 (SD 16.4), 57.7% were male and 5.7% had a chronic respiratory disease (CRD). Mean 4C-MS was slightly higher in the second wave (8.6 [2.9] vs 8.1 [3.1] p=0.018) indicating more severe disease. Intensive care unit (ICU) admission rate was lower at the second wave (7.5% vs 11.8%, p=0.02) alongside with shorter stay (median 12.3 vs. 5.1 days p=0.003). Death rates at first and second wave were 18.9% and 17.6% respectively (p=0.456).

The modified 4C-MS showed an excellent prognostic value for assessing the risk of death (AUC 0.83).

After adjusting for the 4C-MS  at admission, COVID-19 risk of death tended to be lower at second vs first wave (OR 0.69 [0.46 - 1.03] p=0.07). Having a CRD was associated with higher risk of death (adjusted OR 2.82 [1.41- 5.65] p=0.003).

Conclusions: Despite higher mean 4C-MS and lower ICU admission rate, COVID-19 mortality tended to be lower at the second wave as compared to the first wave suggesting improvement of care.