SOFA-2 Score in Defining Sepsis
The SOFA-2 score is a critical tool for defining sepsis as it measures life-threatening organ dysfunction caused by a dysregulated host response to infection, with an increase of 2 or more points representing organ dysfunction that defines sepsis according to the Sepsis-3 criteria. 1, 2
Components and Scoring of SOFA
The SOFA score evaluates dysfunction across six organ systems, with each system scored from 0-4 points (total possible range 0-24) 3:
- Respiratory system: PaO2/FiO2 ratio
- Cardiovascular system: Mean arterial pressure and vasopressor requirements
- Neurological system: Glasgow Coma Scale
- Renal system: Creatinine levels and urine output
- Hepatic system: Bilirubin levels
- Coagulation system: Platelet count
The SOFA-2 score has updated thresholds that better describe organ dysfunction distribution and associated mortality (AUROC 0.79) compared to the original SOFA score (AUROC 0.77) 4
Clinical Significance in Defining Sepsis
According to the Sepsis-3 definition, sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, with organ dysfunction represented by an increase in SOFA score of 2 points or more 1
The SOFA score was originally developed to sequentially assess the degree of multi-organ failure in critically ill patients with sepsis and has been widely validated across healthcare settings 3, 5
The European Medicines Agency has accepted that a change in SOFA score is an acceptable surrogate marker of efficacy in exploratory trials of novel therapeutic agents in sepsis 5
Quick SOFA (qSOFA) and Screening
The qSOFA score includes three clinical variables: Glasgow Coma Scale score of 13 or less, systolic blood pressure of 100 mm Hg or less, and respiratory rate 22/min or greater 1
Patients with at least 2 of these 3 qSOFA criteria may be prone to poor outcomes typical of sepsis and should be further evaluated using the complete SOFA score 1
While qSOFA serves as a bedside screening tool, the full SOFA score provides a more comprehensive assessment of organ dysfunction 1, 6
Prognostic Value
The SOFA score has high discriminative ability in predicting mortality in sepsis patients, with an area under the ROC curve of approximately 0.75 3, 7
When the SOFA score is >11, its sensitivity and negative predictive values for sepsis diagnosis are both 100% 7
For predicting in-hospital mortality, a SOFA score >9 has a sensitivity of 65.8% and specificity of 75.5% 7
An increase in SOFA score (ΔSOFA) of ≥2 points from day 1 to day 3 is associated with significantly higher mortality rates 8
Clinical Application
Regular, repeated scoring of SOFA enables monitoring of disease progression throughout a patient's ICU stay 3, 2
The SOFA score should be calculated on admission and then sequentially to monitor progression of organ dysfunction and response to treatment 2
For patients with suspected sepsis, SOFA scores guide management decisions and resource allocation 2
Limitations and Considerations
The SOFA score does not incorporate gastrointestinal or immune dysfunction due to insufficient data and lack of content validity 2, 4
Unlike other scoring systems such as APACHE II, SOFA does not consider the patient's age or comorbidities 3, 9
SOFA is not suitable for categorizing patients with low-moderate severity without sepsis or organ failure in the first 24 hours of hospital admission 3
Standardization between different assessors in widespread centers is key to detecting response to treatment when using SOFA as an outcome in sepsis clinical trials 5