What are the diagnostic criteria for sepsis and septic shock?

Sepsis vs Septic Shock Diagnostic Criteria

Use the Sepsis-3 definitions: sepsis is life-threatening organ dysfunction (≥2-point SOFA increase) from dysregulated host response to infection, while septic shock requires persistent hypotension needing vasopressors to maintain MAP ≥65 mmHg AND lactate >2 mmol/L despite adequate fluid resuscitation. 1

Sepsis Diagnostic Criteria

Sepsis requires documented or suspected infection PLUS evidence of organ dysfunction, operationalized as an increase in Sequential Organ Failure Assessment (SOFA) score of ≥2 points, which correlates with in-hospital mortality >10%. 1

SOFA Score Components (1-4 points each system):

• Respiratory: PaO2/FiO2 ratio <400 (1 point) to <100 with mechanical ventilation (4 points) 2
• Coagulation: Platelets <150,000 (1 point) to <20,000 (4 points) 2
• Hepatic: Bilirubin 1.2-1.9 mg/dL (1 point) to >12.0 mg/dL (4 points) 2
• Cardiovascular: MAP <70 mmHg (1 point) to high-dose vasopressors (4 points) 2
• Neurologic: Glasgow Coma Scale 13-14 (1 point) to <6 (4 points) 2
• Renal: Creatinine 1.2-1.9 mg/dL (1 point) to >5.0 mg/dL or urine output <200 mL/day (4 points) 2

Alternative Diagnostic Approach (Surviving Sepsis Campaign)

For settings where SOFA scoring is impractical, sepsis can be diagnosed using documented/suspected infection plus ANY combination of the following categories: 2, 3

General variables:

• Fever >38.3°C or hypothermia <36°C 2, 3
• Heart rate >90/min 2, 3
• Respiratory rate >20/min or tachypnea 2, 3
• Altered mental status 2, 3
• Significant edema or positive fluid balance (>20 mL/kg over 24h) 2, 3
• Hyperglycemia (>140 mg/dL) without diabetes 2, 3

Inflammatory variables:

• Leukocytosis (WBC >12,000/μL), leukopenia (WBC <4,000/μL), or >10% bands 2, 3
• Elevated C-reactive protein or procalcitonin (>2 SD above normal) 2, 3

Hemodynamic variables:

• Arterial hypotension (SBP <90 mmHg, MAP <70 mmHg, or SBP decrease >40 mmHg) 2, 3

Organ dysfunction variables:

• Arterial hypoxemia (PaO2/FiO2 <300) 2, 3
• Acute oliguria (urine output <0.5 mL/kg/h for ≥2h despite adequate fluids) 2, 3
• Creatinine increase >0.5 mg/dL 2, 3
• Coagulation abnormalities (INR >1.5 or elevated aPTT) 2, 3
• Ileus (absent bowel sounds) 2, 3
• Thrombocytopenia (platelets <100,000/μL) 2, 3
• Hyperbilirubinemia (total bilirubin >4 mg/dL) 2, 3

Tissue perfusion variables:

• Hyperlactatemia (>1 mmol/L) 2, 3
• Decreased capillary refill or mottling 2, 3

Quick SOFA (qSOFA) for Rapid Screening

Outside ICU settings, use qSOFA to rapidly identify high-risk patients—≥2 of the following predicts poor outcomes: 1

• Respiratory rate ≥22/min 1
• Altered mentation 1
• Systolic blood pressure ≤100 mmHg 1

Important caveat: qSOFA is a screening tool, NOT a diagnostic criterion for sepsis itself. 1, 4 A negative qSOFA does not exclude sepsis, and positive qSOFA should prompt full SOFA assessment. 4

Septic Shock Diagnostic Criteria

Septic shock is a subset of sepsis requiring ALL three criteria: 1, 5

1. Persistent hypotension requiring vasopressors to maintain MAP ≥65 mmHg 1, 5
2. Serum lactate >2 mmol/L (>18 mg/dL) 1, 5
3. Despite adequate fluid resuscitation 1, 5

This combination is associated with hospital mortality rates >40%. 1 The elevated lactate threshold distinguishes septic shock from sepsis with hypotension alone, reflecting profound circulatory and cellular-metabolic abnormalities. 1, 5

Key Distinction from Older Definitions

The term "severe sepsis" has been eliminated as redundant—all sepsis is now considered life-threatening by definition. 1 The Sepsis-2 criteria that relied heavily on SIRS (systemic inflammatory response syndrome) are obsolete because SIRS criteria lacked specificity and sensitivity. 1, 6

Practical Clinical Algorithm

Step 1: Identify suspected or documented infection 1

Step 2: If outside ICU, apply qSOFA—if ≥2 positive, proceed to full assessment 1

Step 3: Calculate SOFA score or assess for presence of organ dysfunction variables 1, 2

Step 4: If SOFA increase ≥2 points → Diagnose SEPSIS 1

Step 5: If sepsis present, check for shock criteria:

• Requiring vasopressors for MAP ≥65 mmHg? 1
• Lactate >2 mmol/L? 1
• After adequate fluids? 1

If all three present → Diagnose SEPTIC SHOCK 1

Common Pitfalls

Do not wait for hypotension to diagnose sepsis—organ dysfunction without hypotension still qualifies as sepsis. 1 Conversely, hypotension alone without elevated lactate does not meet septic shock criteria under Sepsis-3 definitions. 1

Lactate >4 mmol/L is no longer part of organ dysfunction criteria for defining sepsis—it is reserved specifically for septic shock diagnosis. 2

In pediatric populations, diagnostic criteria differ slightly, requiring signs of inflammation plus infection with hyper/hypothermia, tachycardia, and at least one indicator of altered organ function (altered mental status, hypoxemia, increased lactate, or bounding pulses). 2, 3