How is the SOFA-2 (Sequential Organ Failure Assessment-2) score used to diagnose sepsis?

SOFA-2 Score in Diagnosing Sepsis

The SOFA-2 (Sequential Organ Failure Assessment) score is the primary diagnostic tool for sepsis, with an increase of ≥2 points in the SOFA score indicating organ dysfunction in the context of suspected infection, which defines sepsis according to the Sepsis-3 criteria. 1

SOFA Score Components and Calculation

The SOFA score evaluates six organ systems, with each assigned 0-4 points based on the degree of dysfunction:

• Respiratory system: PaO2/FiO2 ratio assessment 1
• Cardiovascular system: Blood pressure and vasopressor requirements 1
• Hepatic system: Bilirubin levels 1
• Coagulation: Platelet count 1
• Renal system: Creatinine levels or urine output 1
• Neurological system: Glasgow Coma Scale 1, 2

Diagnosing Sepsis Using SOFA-2

• Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection 1
• A SOFA score increase of ≥2 points from baseline in the presence of infection confirms sepsis diagnosis 2
• Baseline SOFA is assumed to be zero in patients without pre-existing organ dysfunction 2
• The SOFA score has demonstrated high discriminative ability (AUC=0.89) in predicting sepsis 3
• When the SOFA score is >11, its sensitivity and negative predictive values for sepsis are both 100% 3

Risk Stratification and Mortality Prediction

• SOFA scores >9 are associated with higher in-hospital mortality (sensitivity 65.8%, specificity 75.5%) 3
• SOFA scores >11 predict emergency department mortality with 63.5% sensitivity and 78.8% specificity 3
• Mean SOFA score (calculated from serial measurements) has shown superior performance (sensitivity 93.65%, specificity 100%) compared to single SOFA measurements in predicting mortality 4

Quick SOFA (qSOFA) as a Screening Tool

• qSOFA consists of three clinical criteria: respiratory rate ≥22/min, altered mentation, and systolic BP ≤100 mmHg 5
• qSOFA ≥2 indicates increased risk of poor outcomes and should prompt further assessment 1
• qSOFA has limited sensitivity but good specificity for predicting sepsis-related mortality 6
• Patients with positive qSOFA score (≥2) have significantly higher odds of dying at 7 days (OR: 3.9) and 28 days (OR: 6.9) 6

National Early Warning Score 2 (NEWS2) Integration

• NEWS2 is recommended for initial risk stratification in suspected sepsis 5
• NEWS2 interpretation for sepsis risk:
  • Score of 0: Very low risk 5
  • Score of 1-4: Low risk 5
  • Score of 5-6: Moderate risk 5
  • Score of ≥7: High risk 5
• A score of 3 in any single parameter may indicate increased risk from sepsis 5

Sepsis-Induced Coagulopathy (SIC)

• SIC is a specific complication of sepsis affecting the coagulation system 1
• SIC diagnostic criteria include:
  • Platelet count (1 point for 100-150×10⁹/L, 2 points for <100×10⁹/L) 5
  • PT-INR (1 point for 1.2-1.4,2 points for >1.4) 5
  • SOFA score (1 point for SOFA=1,2 points for SOFA ≥2) 5
• A total SIC score ≥4 confirms diagnosis 5
• SIC has approximately 30% mortality and may progress to overt DIC 5

Clinical Implementation

• Re-evaluate SOFA scores periodically to monitor disease progression and response to treatment 5
• Frequency of re-evaluation should be based on risk level:
  • High risk: Every 30 minutes 5
  • Moderate risk: Every hour 5
  • Low risk: Every 4-6 hours 5
• Consider both absolute SOFA score and changes in SOFA score when evaluating patients 2

Common Pitfalls and Caveats

• SOFA scores should be interpreted in the context of the patient's baseline physiology and comorbidities 5
• Assuming a baseline SOFA of zero may overestimate the score change in patients with chronic organ dysfunction 2
• The SOFA score alone does not diagnose sepsis - documented or suspected infection is a prerequisite 1
• Laboratory values may not be immediately available, potentially delaying SOFA score calculation 2
• Standardization between different assessors is crucial for accurate SOFA scoring in clinical trials 2