Development and Validation of the Sequential Organ Failure Assessment (SOFA)-2 Score

Acute dysfunction of vital organs is the hallmark of critical illness. The Sequential Organ Failure Assessment (SOFA) score, the most widely adopted approach to describe organ dysfunction, has not been updated in 30 years and therefore may not appropriately capture current clinical practice and outcomes.

To inform the data-driven component of an updated score (SOFA-2) in varied geographical and resource settings (stages 6-8) after expert input via a modified Delphi process (stages 1-5).

A federated analysis was performed on data collected from adult patients admitted to 1319 intensive care units (ICUs) in 9 countries (Australia, Austria, Brazil, France, Italy, Japan, Nepal, New Zealand, United States) between 2014 and 2023. Four representative multicenter cohorts containing data from 2 098 356 patients were used for data-driven score development and internal validation. External validation was performed on 6 cohorts containing data from 1 241 114 patients.

Content validity for organ dysfunction identified through the modified Delphi process should be reflected by predictive validity using the area under the receiver operating characteristic (AUROC) curve of the score measured on the first ICU day (higher scores indicate worse organ dysfunction).

Of 3.34 million patient encounters, 270 108 (8.1%) died in the ICU (range, 4.5% to 20.5% across the 10 cohorts). SOFA-2 modified the 6 organ systems of the original SOFA score (brain, respiratory, cardiovascular, liver, kidney, hemostasis), including new variables and revised thresholds that better describe the organ dysfunction distribution from 0 to 4 points and their associated mortality (SOFA-2 AUROC, 0.79; 95% CI, 0.76-0.81; SOFA-1 AUROC, 0.77; 95% CI, 0.74-0.81). Evaluation of sequential SOFA-2 data from ICU day 1 to day 7 maintained its predictive validity. Insufficient data and lack of content validity precluded incorporation of gastrointestinal and immune dysfunction scores into SOFA-2.

The SOFA-2 score, updated to include contemporary organ support treatments and new score thresholds, describes organ dysfunction in a large, geographically and socioeconomically diverse population of critically ill adults.