Clinical Risk Score for Predicting Oxygen Administration Required among Patients with SARS-CoV-2 Omicron Strains

[Background] With an increase in the number of patients with COVID-19, clinics and medical hospitals, particularly those providing primary health care have an increasing role in the appropriate and efficient triage of patients with COVID-19. [Purpose] To identify predicting variables for the requirement for oxygen administration within 7 days among patients with SARS-CoV-2 Omicron strains. To establish a clinical risk score for predicting oxygen administration required within 7 days. [Patients and Methods] A retrospective observational study of 584 outpatients with COVID-19 confirmed by polymerase chain reaction (PCR) test visited Sasebo Chuo Hospital between 28 April 2022 and 18 August 2022. Analyses were conducted after adjustment for background factors of age and sex with propensity score matching. We used Fisher test for nominal variables and Kruskal–Wallis test for continuous variables. [Results] After adjustment for the background factors of age and sex, body temperature (p < 0.001), respiratory rate (p = 0.007), SpO 2 (p < 0.001), and confirmation of pneumonia on computerized tomography (CT) (p = 0.032) were found to be significantly associated with oxygen administration requirement within 7 days. The positive/negative likelihood for requiring oxygen administration within 7 days of the risk score based on body temperature, age, respiratory rate and SpO 2 are 2.9/0.0 with the cut-off value of 5 points and 18/0.4 with the cut-off value of 10 points. The area under the ROC curve of the risk score was 0.937 (95% Confidence Interval [CI]: 0.900-0.974). [Discussion] Using the risk score which does not require a detailed history interview or CT scan but only age and vital signs may help make an efficient referral to a hospital where the patient can be admitted. [Conclusions] Elevated body temperature, advanced age, increased respiratory rate, decreased SpO 2, and pneumonia on CT were significantly associated with oxygen administration required within 7 days in the study population. The risk score using temperature, age, respiratory rate, and SpO 2 could efficiently assess the risk of oxygen administration required within 7 days with good accuracy. [Trial registration] 584 patients were retrospectively registered. The trial registration number is 2022-15. The date of registration is 26 April, 2022.