Sepsis Diagnostic Criteria
Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, operationalized as an acute increase in Sequential Organ Failure Assessment (SOFA) score of ≥2 points from baseline, which correlates with in-hospital mortality >10%. 1, 2, 3
Core Diagnostic Framework
SOFA Score Requirements
- An increase of ≥2 points in SOFA score is required to diagnose sepsis in patients with suspected or confirmed infection 1, 2, 3
- The SOFA score assesses six organ systems (0-4 points each): respiratory, cardiovascular, hepatic, coagulation, renal, and neurological 1
- Baseline SOFA score is assumed to be zero in patients without pre-existing organ dysfunction 3
Quick SOFA (qSOFA) Bedside Screening
qSOFA ≥2 points identifies high-risk patients with suspected infection who require immediate full SOFA assessment and consideration for ICU-level care 1, 2, 4, 3
qSOFA criteria (1 point each):
- Respiratory rate ≥22 breaths/minute 1, 3, 5
- Altered mental status (Glasgow Coma Scale <15) 1, 3
- Systolic blood pressure ≤100 mmHg 1, 4, 3
SOFA Score Components in Detail
Respiratory System
- PaO₂/FiO₂ <400: 1 point 1
- PaO₂/FiO₂ <300: 2 points 1
- PaO₂/FiO₂ <200 with mechanical ventilation: 3 points 1
- PaO₂/FiO₂ <100 with mechanical ventilation: 4 points 1
Cardiovascular System
- Mean arterial pressure (MAP) <70 mmHg: 1 point 1
- Dopamine ≤5 mcg/kg/min or dobutamine (any dose): 2 points 1
- Dopamine >5 OR epinephrine ≤0.1 OR norepinephrine ≤0.1 mcg/kg/min: 3 points 1
- Dopamine >15 OR epinephrine >0.1 OR norepinephrine >0.1 mcg/kg/min: 4 points 1
Other Organ Systems
- Hepatic: Bilirubin >1.2 mg/dL scores points 1
- Coagulation: Platelets <150,000/μL scores points 1
- Renal: Creatinine >3.5 mg/dL or urine output <500 mL/day scores maximum points 1
- Neurological: Glasgow Coma Scale assessment 1
Septic Shock Criteria
Septic shock is identified when patients meet BOTH of the following despite adequate fluid resuscitation: 1, 3
This combination is associated with hospital mortality rates >40% 3
Clinical Implementation Algorithm
Step 1: Identify Suspected Infection
- Any patient with clinical suspicion of infection should be evaluated 1
Step 2: Calculate qSOFA at Bedside
- Assess respiratory rate, blood pressure, and mental status 1, 3
- If qSOFA ≥2: Proceed immediately to full SOFA assessment and consider ICU-level care 1, 2
Step 3: Calculate Full SOFA Score
Step 4: Assess for Septic Shock
- Check if vasopressors needed for MAP ≥65 mmHg 1
- Measure lactate (>2 mmol/L confirms shock if on vasopressors) 1
Step 5: Serial Monitoring
- Recalculate SOFA scores every 48-72 hours to track organ dysfunction trajectory 2
- For high-risk patients (qSOFA ≥2), reassess every 30 minutes 1
Important Caveats and Context
Obsolete Terminology
- The term "severe sepsis" is obsolete and should not be used 1, 2
- SIRS (Systemic Inflammatory Response Syndrome) criteria are no longer required for sepsis diagnosis 2, 3
Performance Characteristics by Setting
ICU Setting:
- SOFA demonstrates superior discrimination (AUROC 0.74) compared to qSOFA (AUROC 0.66) or SIRS (AUROC 0.64) for predicting in-hospital mortality 5
- qSOFA has high specificity (96.1%) but poor sensitivity (29.7%) for organ dysfunction 6
Non-ICU Setting:
- qSOFA demonstrates better discrimination (AUROC 0.81) than SOFA (AUROC 0.79) for predicting mortality outside the ICU 5
- qSOFA ≥2 predicts 3- to 14-fold increase in hospital mortality across baseline risk deciles 5
Alternative Risk Stratification: NEWS2
- The National Institute for Health and Care Excellence (NICE) recommends NEWS2 for initial risk stratification in emergency department settings 1
- NEWS2 ≥7: High risk—reassess every 30 minutes, antibiotics within 1 hour 1
- NEWS2 5-6: Moderate risk—reassess every hour, antibiotics within 3 hours 1
- NEWS2 1-4: Low risk—reassess every 4-6 hours, antibiotics within 6 hours 1
- A single NEWS2 parameter scoring 3 points signals increased sepsis risk regardless of total score 1