What are the Sepsis‑3 criteria for diagnosing sepsis and septic shock?

Sepsis-3 Criteria

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, operationalized by an increase in the Sequential Organ Failure Assessment (SOFA) score of 2 points or more. 1, 2, 3

Core Definitions

Sepsis

• Suspected or confirmed infection PLUS
• SOFA score increase ≥2 points from baseline
• This combination is associated with in-hospital mortality >10% 3
• The term "severe sepsis" is now obsolete and should not be used 1, 2

Septic Shock

Septic shock is a subset of sepsis requiring BOTH of the following criteria: 1, 2, 3

1. Vasopressor requirement to maintain mean arterial pressure (MAP) ≥65 mmHg
2. Serum lactate >2 mmol/L (>18 mg/dL) after adequate fluid resuscitation
3. In the absence of hypovolemia

This combination is associated with hospital mortality rates >40% 3, 4

Quick SOFA (qSOFA) for Rapid Screening

For bedside screening of patients with suspected infection outside the ICU, use qSOFA—a positive score is ≥2 of the following 3 criteria: 1, 2

• Respiratory rate ≥22/min
• Altered mental status (Glasgow Coma Scale ≤13 or any alteration in mentation)
• Systolic blood pressure ≤100 mmHg

Important Caveats About qSOFA

• qSOFA does NOT define sepsis—it is a screening tool to identify patients at higher risk who need further evaluation 2
• qSOFA has high specificity (92.2%) but lower sensitivity (64.9%) for predicting in-hospital mortality 5
• A positive qSOFA should prompt calculation of the full SOFA score and consideration of ICU-level care 5
• qSOFA performed significantly better than SIRS criteria (AUROC 0.80 vs 0.65) in emergency department validation studies 5

Key Changes from Previous Definitions

The Sepsis-3 criteria represent a fundamental shift from the 2001 Sepsis-2 definitions: 1, 2, 3

• Eliminated SIRS criteria as a requirement for sepsis diagnosis (SIRS had poor specificity at 23.6%) 6
• Removed "severe sepsis" as a category—it is now redundant 1, 2
• Shifted focus from inflammation to organ dysfunction as the defining feature
• Lactate >2 mmol/L is now required for septic shock diagnosis (not just elevated lactate) 2, 4

Clinical Application Algorithm

When evaluating a patient with suspected infection:

1. Calculate qSOFA at bedside (≥2 positive = high risk)
2. If qSOFA ≥2: Calculate full SOFA score
3. If SOFA increase ≥2 points: Diagnose sepsis
4. If sepsis present, assess for shock:
   • Requiring vasopressors for MAP ≥65 mmHg? AND
   • Lactate >2 mmol/L after fluids? AND
   • Hypovolemia excluded?
   • If all YES → Septic shock

Common Pitfalls to Avoid

• Do not wait for SIRS criteria—they are no longer part of the definition and delay recognition 3, 5
• Do not diagnose septic shock based on hypotension alone—both vasopressor requirement AND elevated lactate are mandatory 2, 4
• Do not use qSOFA as the sole diagnostic criterion—it is for screening, not diagnosis 2
• Remember baseline SOFA matters—the increase of ≥2 points is from the patient's baseline, which may be elevated in chronic illness 3

Prognostic Implications

Mortality escalates significantly with each level: 2, 7

• Infection without sepsis: 1.2% mortality
• Sepsis (SOFA ≥2): 13% in-hospital mortality
• Septic shock: 40-67.8% mortality depending on the cohort

Patients meeting Sepsis-3 septic shock criteria had higher mortality (40.9% vs 33.5%) compared to those meeting older SIRS-based shock criteria, validating the improved prognostic accuracy of the new definition 6.