What is the SOFA-2 (Sequential Organ Failure Assessment-2) score?

SOFA-2 Score: An Updated Tool for Assessing Organ Dysfunction in Critical Illness

The SOFA-2 score is an updated version of the Sequential Organ Failure Assessment tool that evaluates dysfunction across six organ systems (brain, respiratory, cardiovascular, liver, kidney, and hemostasis) to assess severity of critical illness, with recent modifications to better reflect contemporary clinical practice and outcomes. 1

Overview of SOFA-2

• SOFA-2 was developed through a rigorous process involving expert consensus via a modified Delphi process and data-driven validation using over 3.34 million patient encounters from 1319 ICUs across 9 countries 1, 2
• Like the original SOFA, it evaluates six organ systems with scores ranging from 0-4 for each system (total possible score 0-24), with higher scores indicating worse organ dysfunction 3, 1
• The SOFA-2 score demonstrates improved predictive validity for mortality compared to the original SOFA (AUROC 0.79 vs 0.77) 1

Components and Scoring

• Brain (formerly Central Nervous System): Evaluates neurological status using the Glasgow Coma Scale 3, 2
• Respiratory: Assesses oxygenation primarily through PaO2/FiO2 ratio; when arterial blood gases are unavailable, SpO2/FiO2 ratio can be used as a validated alternative 4, 2
• Cardiovascular: Measures hemodynamic stability and need for vasopressor support 3, 2
• Liver: Evaluates hepatic function through bilirubin levels 3, 2
• Kidney (formerly Renal): Assesses kidney function through creatinine levels and urine output 3, 2
• Hemostasis (formerly Coagulation): Evaluates coagulation status primarily through platelet count 3, 2

Key Improvements in SOFA-2

• Updated thresholds for organ dysfunction scoring to better reflect the distribution of dysfunction severity and associated mortality 1
• Incorporation of contemporary organ support treatments and interventions 1, 2
• Addition of alternative variables for settings where laboratory data or certain interventions may be inaccessible or not indicated 2
• Maintained the six original organ systems but renamed some categories for clarity (e.g., central nervous system to brain, renal to kidney) 2

Clinical Utility

• SOFA-2 allows for sequential monitoring of patients throughout their ICU stay, enabling clinicians to track disease progression 5, 3
• Regular, repeated scoring provides valuable information about evolving organ dysfunction and response to treatment 5, 3
• The score is particularly useful for research purposes, audit, and comparing outcomes across different ICU populations 5, 6

Limitations and Considerations

• SOFA-2 does not incorporate gastrointestinal or immune dysfunction due to insufficient data and lack of content validity 1, 2
• Like the original SOFA, it does not consider patient age or comorbidities, unlike other scoring systems such as APACHE II 3, 6
• Not suitable for categorizing patients with low-moderate severity without sepsis or organ failure in the first 24 hours of hospital admission 3
• The original SOFA's cardiovascular component had lower association with mortality compared to other organ systems, which has been addressed in SOFA-2 7, 2

Practical Application

• SOFA-2 can be calculated on admission and then sequentially to monitor progression of organ dysfunction 3, 1
• The score is valuable for predicting outcomes in critically ill patients, particularly those with sepsis 5, 8
• When implementing SOFA-2 in research protocols, it's important to clearly define primary and secondary outcomes and establish standardized protocols for collecting physiological parameters 6
• For patients with suspected sepsis, SOFA-2 can help guide management decisions and resource allocation 5, 8