SOFA score performs worse than age for predicting mortality in patients with COVID-19
Abstract
The use of the Sequential Organ Failure Assessment (SOFA) score, originally developed to describe disease morbidity, is commonly used to predict in-hospital mortality. During the COVID-19 pandemic, many protocols for crisis standards of care used the SOFA score to select patients to be deprioritized due to a low likelihood of survival. A prior study found that age outperformed the SOFA score for mortality prediction in patients with COVID-19, but was limited to a small cohort of intensive care unit (ICU) patients and did not address whether their findings were unique to patients with COVID-19. Moreover, it is not known how well these measures perform across races.
In this retrospective study, we compare the performance of age and SOFA scores in predicting in-hospital mortality across two cohorts: a cohort of 2,648 consecutive adult patients diagnosed with COVID-19 who were admitted to a large academic health system in the northeastern United States over a 4-month period in 2020 and a cohort of 75,601 patients admitted to one of 335 ICUs in the eICU database between 2014 and 2015.
Among the COVID-19 cohort, age (area under receiver-operating characteristic curve (AU-ROC) 0.795, 95% CI 0.762, 0.828) had a significantly better discrimination than SOFA score (AU-ROC 0.679, 95% CI 0.638, 0.721) for mortality prediction. Conversely, age (AU-ROC 0.628 95% CI 0.608, 0.628) underperformed compared to SOFA score (AU-ROC 0.735, 95% CI 0.726, 0.745) in non-COVID-19 ICU patients in the eICU database. There was no difference between Black and White COVID-19 patients in performance of either age or SOFA Score. Our findings bring into question the utility of SOFA score-based resource allocation in COVID-19 crisis standards of care.
Author Summary
The COVID-19 pandemic has prompted hospitals to develop protocols for allocating resources if the number of patients exceed their capacity in order to save as many lives as possible. Many of these protocols use the Sequential Organ Failure Assessment (SOFA) score to identify patients who are unlikely to survive and thus should be deprioritized for care. There are concerns that the SOFA score may not accurately predict mortality in patients with COVID-19 or perform better in one racial group over another. We asked whether a simple measure, patient age, could better predict mortality than SOFA score in a group of adult patients admitted to a large academic health system in 2020. To see if any findings are unique to patients with COVID-19, we performed the same analysis in a group of adult patients taken from the eICU database, a large publicly available dataset that was collected prior to the COVID-19 pandemic. We found that age was better than SOFA score at predicting patient mortality in patients with COVID-19, but not in patients without COVID. For COVID-19, neither age or SOFA score performed better in one racial group over another. Caution is needed when applying an established disease severity index model to a new illness.
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