The Sequential Organ Failure Assessment (SOFA) score is a clinical tool designed to track a patient’s status during their stay in the intensive care unit (ICU). Initially introduced in the 1990s by the European Society of Intensive Care Medicine, the SOFA score quantifies the degree of dysfunction across six major organ systems. By assigning points based on objective clinical and laboratory measurements, the SOFA score provides a standardized way to monitor disease severity, assess the risk of morbidity and mortality, and guide treatment decisions.
Today, the SOFA score is widely used in critical care, sepsis management, and clinical research. A rise in SOFA score of ≥ 2 points is a key diagnostic criterion for sepsis according to the Sepsis-3 definitions, making it integral to modern critical care practice.
Organ Systems Assessed
The SOFA score evaluates dysfunction across six organ systems: respiratory, coagulation, liver, cardiovascular, central nervous system, and renal. Each system is graded from 0 (normal) to 4 (severe dysfunction).
| Organ System | Variable | 0 | 1 | 2 | 3 | 4 |
|---|---|---|---|---|---|---|
| Respiratory | PaO₂/FiO₂ (mmHg) | > 400 | ≤ 400 | ≤ 300 | ≤ 200 (with resp. support) | ≤ 100 (with resp. support) |
| Coagulation | Platelets (×10⁹/L) | > 150 | ≤ 150 | ≤ 100 | ≤ 50 | ≤ 20 |
| Liver | Bilirubin (mg/dL) | < 1.2 | 1.2–1.9 | 2.0–5.9 | 6.0–11.9 | ≥ 12.0 |
| Cardiovascular | Blood pressure/vasopressors | MAP ≥ 70 mmHg | MAP < 70 mmHg | Dopamine ≤ 5 or dobutamine | Dopamine > 5, or epinephrine ≤ 0.1, or norepinephrine ≤ 0.1 | Dopamine > 15, or epinephrine > 0.1, or norepinephrine > 0.1 |
| CNS | Glasgow Coma Scale (GCS) | 15 | 13–14 | 10–12 | 6–9 | < 6 |
| Renal | Creatinine (mg/dL) or urine output | < 1.2 | 1.2–1.9 | 2.0–3.4 | 3.5–4.9 or urine < 500 mL/day | ≥ 5.0 or urine < 200 mL/day |
Interpretation
The total SOFA score is obtained by summing the points for each organ system. The score can range from 0 (no organ dysfunction) to 24 (severe multi-organ failure). Higher scores correlate with higher mortality:
- 0–6: Low risk of organ failure and mortality
- 7–9: Moderate risk
- 10–12: High risk, significant mortality
- > 12: Very high risk, poor prognosis
Increases in SOFA score during ICU stay are more predictive of mortality than the absolute score at admission. A rise of ≥ 2 points suggests significant clinical deterioration and is one of the key criteria for diagnosing sepsis under Sepsis-3.
Clinical Significance
The SOFA score is integral to critical care management for several reasons:
- Sepsis diagnosis: A change in SOFA score is a defining feature of sepsis, making it essential for early recognition and treatment.
- Prognostication: Provides objective data to predict ICU mortality and guide family discussions.
- Monitoring disease progression: Tracks dynamic changes in organ function during hospitalization.
- Research and trials: Widely used in critical care research to standardize severity assessments.
- Resource allocation: Helps prioritize critical care interventions and monitoring intensity.
Indications for Use
The SOFA score is used in:
- Patients admitted to the ICU for sepsis, shock, or multi-organ dysfunction.
- Clinical monitoring of critically ill patients over time.
- Standardizing outcomes in sepsis and critical care research studies.
- Early recognition of deterioration in patients with infections, trauma, or severe illness.
Limitations
Despite its utility, the SOFA score has limitations:
- Complexity: Requires multiple laboratory values and monitoring equipment, limiting use outside ICU settings.
- Time sensitivity: Some parameters (like bilirubin or platelet count) may take time to process, delaying scoring.
- Baseline conditions: Chronic comorbidities (e.g., cirrhosis, chronic kidney disease) may elevate baseline scores without reflecting acute illness severity.
- Not disease-specific: SOFA does not identify the underlying cause of organ dysfunction.