A 4C mortality score based dichotomic rule supports Emergency Department discharge of COVID-19 patients.

Background: For COVID-19 patients evaluated in the Emergency Department (ED), decision on hospital admission vs. home discharge is challenging. The 4C mortality score (4CMS) is a prognostication tool integrating key demographic/clinical/biochemical data validated for COVID-19 inpatients. We sought to derive and validate a dichotomic rule based on 4CMS identifying patients with mild outcomes, suitable for safe ED discharge.

Methods: Derivation was performed in a prospective cohort of ED patients with suspected COVID-19 from two centers (April 2020). Validation was pursued in a prospective multicenter cohort of ED patients with confirmed COVID-19 from 6 centers (October 2020 to January 2021). Chest X-ray (CXR) images were independently scored. The primary composite outcome was all-cause 30-day mortality or hospital admission. Secondary outcomes were ED re-visit, oxygen therapy and ventilation.

Results: In a derivation cohort of 838 ED patients with suspected COVID-19, 4CMS≤8 was associated with low outpatient mortality (0.4%) and was thus selected as a feasible discharge rule. In a validation cohort of 521 COVID-19 outpatients, the mean age was 51±17 years; 97 (18.6%) patients had ≥1 CXR infiltrate. The 4CMS had an AUC of 0.82 for the primary outcome and 0.93 for mortality, outperforming other scores (CURB-65, qCSI, qSOFA, NEWS) and CXR. In 474 (91%) patients with 4CMS≤8, the mortality rate was 0.2% and the hospital admission rate was 6.8%, versus 12.8% and 36.2% for 4CMS≥9 (P<0.001). CXR did not provide additional discrimination.

Conclusions: COVID-19 outpatients with 4CMS≤8 have mild outcomes and can be safely discharged from the ED. [NCT0462918].