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

What is the Sequential Organ Failure Assessment (SOFA) Score?

The Sequential Organ Failure Assessment (SOFA) score is a validated clinical tool that evaluates dysfunction across six organ systems—respiratory, cardiovascular, brain, liver, kidney, and hemostasis—with each system scored 0-4 points for a total possible score of 0-24, where higher scores indicate worse organ dysfunction and increased mortality risk. 1

Core Components of the SOFA Score

The SOFA score assesses six major organ systems using specific clinical and biochemical parameters 2:

1. Respiratory System

• Evaluated via PaO2/FiO2 ratio, ranging from 0 (≥400 mmHg) to 4 (<100 mmHg with mechanical ventilation) 1
• When arterial blood gas data are unavailable, SpO2/FiO2 ratio can be substituted as a validated alternative 3

2. Cardiovascular System

• Assessed through mean arterial pressure (MAP) and vasopressor requirements 1
• Scoring ranges from 0 (MAP ≥70 mmHg) to 4 (high-dose dopamine >15 μg/kg/min or high-dose epinephrine/norepinephrine) 2

3. Brain (Neurological)

• Evaluated using hepatic encephalopathy grade in cirrhotic patients or Glasgow Coma Scale in general ICU populations 2
• Ranges from 0 (no encephalopathy) to 4 (Grade IV encephalopathy) 2

4. Liver

• Assessed via serum bilirubin levels 2
• Scoring ranges from 0 (<1.2 mg/dL) to 4 (≥12.0 mg/dL) 2

5. Kidney (Renal)

• Evaluated through serum creatinine levels 2
• Ranges from 0 (<1.2 mg/dL) to 4 (≥5.0 mg/dL) 2

6. Hemostasis (Coagulation)

• Measured primarily by platelet count and INR 2
• Scoring ranges from 0 (INR <1.1) to 4 (INR ≥2.5 or platelets ≤20,000/mm³) 2

Clinical Significance and Interpretation

Score Ranges and Mortality Risk

• SOFA score of 2: Indicates mild single-organ dysfunction with relatively low mortality risk in general ICU populations 1
• SOFA score increase of ≥2 points from baseline: In the presence of documented or suspected infection, this defines sepsis according to Sepsis-3 criteria and triggers immediate broad-spectrum antibiotics within 1 hour, fluid resuscitation, and source control 1, 4
• SOFA scores 7-10: Indicate significant multi-organ dysfunction with substantially increased mortality risk 1
• SOFA score >10: Predicts mortality exceeding 80-90% 1
• SOFA score >11: Associated with >90% mortality 1, 5

Sequential Assessment

• Calculate SOFA score on ICU admission using the most abnormal values from the first 24 hours 1
• Reassess SOFA scores every 48-72 hours throughout the ICU stay to track disease progression and treatment response 1, 4
• The "delta SOFA" (total maximum SOFA score minus admission total SOFA) provides valuable prognostic information about disease trajectory 5

Special Applications

In Cirrhosis and Acute-on-Chronic Liver Failure (ACLF)

The SOFA score was adapted for cirrhotic patients as the CLIF-SOFA score, which forms the basis for diagnosing and grading ACLF 2:

• ACLF Grade Ia: Single renal failure (creatinine ≥2 mg/dL) 2
• ACLF Grade Ib: Single non-kidney organ failure with mild renal dysfunction (creatinine 1.5-1.9 mg/dL) and/or hepatic encephalopathy grade I-II 2
• ACLF Grade II: Two organ failures with 28-day mortality of 32% 2
• ACLF Grade III: Three or more organ failures with 28-day mortality of 78% 2

In Sepsis Management

• A SOFA score increase of ≥2 points from baseline in patients with documented or suspected infection meets Sepsis-3 criteria 1, 4
• This triggers immediate initiation of broad-spectrum antibiotics within 1 hour, aggressive fluid resuscitation, and source control 1
• Screen all septic patients for coagulopathy using the Sepsis-Induced Coagulopathy (SIC) scoring system, which incorporates SOFA score ≥2 as one component 6

Critical Limitations and Pitfalls

What SOFA Does NOT Account For

• Age and comorbidities: Unlike APACHE II scoring systems, SOFA does not consider patient age or pre-existing conditions 1, 4
• Gastrointestinal and immune dysfunction: These organ systems could not be incorporated due to insufficient data and lack of content validity 7, 8

Inappropriate Uses

• Do not use SOFA alone for triage decisions in non-pandemic settings, as it lacks validation for resource allocation at low scores 1
• Do not assume sepsis based solely on SOFA score ≥2 without documented infection 6
• SOFA is a tool to augment, not replace, clinical judgment 6

Recent Updates: SOFA-2

A revised version (SOFA-2) was developed in 2025 to reflect contemporary clinical practice 7, 8:

• Retains the same six organ systems but updates variables and thresholds to better describe current organ support treatments 7, 8
• Maintains predictive validity with AUROC of 0.79 (95% CI, 0.76-0.81) compared to original SOFA AUROC of 0.77 (95% CI, 0.74-0.81) 8
• Incorporates modern vasopressor dosing, mechanical ventilation practices, and organ support devices 7, 8

Practical Application Algorithm

1. On ICU admission: Calculate baseline SOFA score using worst values from first 24 hours 1
2. Every 48-72 hours: Reassess SOFA score to monitor disease trajectory 1, 4
3. If SOFA increases by ≥2 points with infection: Diagnose sepsis and initiate immediate sepsis bundle (antibiotics within 1 hour, fluids, source control) 1
4. If SOFA >10-11: Discuss goals of care and appropriateness of invasive interventions versus palliative measures, as mortality exceeds 90% 6
5. Monitor delta SOFA: Static or increasing scores signal treatment failure requiring escalation of care 6, 5