Rationale and Methodological Approach Underlying the Development of the Sequential Organ Failure Assessment (SOFA)–2 Score

Importance The Sequential Organ Failure Assessment (SOFA) score was published in 1996 to describe organ dysfunction in critically ill adult patients in a readily quantifiable and sequential manner. Considerable changes have occurred over the last 3 decades in the use of organ support drugs and devices and in patient outcomes, necessitating revision of the score. Objectives To develop definitions of organ dysfunction that reflect current understanding and to identify representative variables to generate a revised SOFA score (SOFA-2) of individual organ dysfunction. Evidence Review A task force of experts in intensive care medicine and epidemiology generated definitions of organ dysfunction, identified relevant variables (physiological and laboratory data specific to the organ system, pharmacological and mechanical organ support), and proposed a 0 to 4–point grading of dysfunction severity through meetings, Delphi processes, and explicit rules, informed by data synthesis, including systematic reviews and meta-analysis. Variables were tested in 2 validation exercises using separate datasets totaling 3.34 million patients within 10 representative databases from diverse geographical and socioeconomic settings to assess distribution and predictive validity (mortality at intensive care unit discharge). Findings A total of 60 experts participated, with 18 (30%) female participants. Overall, 65 countries were represented, with 33 (51%) from Europe and Central Asia, 13 (20%) from North America; and 8 (12%) from Latin America and the Caribbean. The physiological variables within the 6 organ systems used in the original SOFA score were retained, although some categories were renamed (ie, central nervous system was changed to brain, renal to kidney, coagulation to hemostasis, and hepatic to liver). Revisions of organ support drug and device variables were made to reflect current practice. Alternative variables were added for instances when laboratory data and/or organ support interventions would be inaccessible (eg, in some low-resource settings) or not indicated (eg, ceiling of treatment). Some point cutoff thresholds were modified based on evidence from systematic reviews and data analyses. Scores could not be developed for 2 additional organ systems (gastrointestinal and immune) due to insufficient data, complexity, or lack of content and predictive validity for the variables assessed. Explicit rules were developed to facilitate scoring consistency. Conclusions and Relevance Through a methodologically robust development process, the SOFA-2 score offers updated definitions to describe organ dysfunction in adult patients requiring critical care and readily quantifiable criteria to grade the degree of dysfunction in individual organ systems. This score considers contemporaneous changes in patient management and outcomes.