What are the criteria for diagnosing sepsis?

Sepsis Diagnostic Criteria

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, with diagnosis based primarily on the Sequential Organ Failure Assessment (SOFA) score and clinical evidence of infection. 1, 2

Primary Diagnostic Tools

• The Sequential Organ Failure Assessment (SOFA) score is the primary tool for diagnosing sepsis-related organ dysfunction, with a score increase of ≥2 points indicating organ dysfunction associated with >10% in-hospital mortality 1, 2
• For rapid bedside assessment, the quick SOFA (qSOFA) score can be used, which includes three criteria: respiratory rate ≥22/min, altered mentation, and systolic blood pressure ≤100 mmHg 2, 3
• The National Early Warning Score 2 (NEWS2) has been shown to be superior to qSOFA for detecting sepsis with organ dysfunction in emergency department settings 1, 4

Clinical Signs and Laboratory Markers

Infection Indicators

• Fever (core temperature >38.3°C) or hypothermia (core temperature <36°C) 5, 6
• Tachycardia (heart rate >90 beats/min or >2 SD above normal for age) 5, 6
• Tachypnea (respiratory rate >20 breaths/min) 6
• Altered mental status 5, 6
• Significant edema or positive fluid balance (>20 mL/kg over 24h) 5, 6
• Hyperglycemia (plasma glucose >140 mg/dL) in the absence of diabetes 5, 6
• Leukocytosis (WBC >12,000/μL), leukopenia (WBC <4,000/μL), or normal WBC with >10% immature forms 5, 6
• Elevated inflammatory markers: C-reactive protein or procalcitonin >2 SD above normal value 5, 6

Organ Dysfunction Markers

• Arterial hypotension (SBP <90 mmHg, MAP <70 mmHg, or SBP decrease >40 mmHg) 5, 6
• Arterial hypoxemia (PaO₂/FiO₂ <300) 5, 6
• Acute oliguria (urine output <0.5 mL/kg/h for at least 2h despite adequate fluid resuscitation) 5, 6
• Creatinine increase ≥0.5 mg/dL 5, 6
• Coagulation abnormalities (INR >1.5 or aPTT >60s) 5, 6
• Ileus (absent bowel sounds) 5, 6
• Thrombocytopenia (platelet count <100,000/μL) 5, 6
• Hyperbilirubinemia (plasma total bilirubin >4 mg/dL) 5, 6
• Hyperlactatemia (>1 mmol/L) 5, 6
• Decreased capillary refill or mottling 5, 6

Severe Sepsis and Septic Shock

• Severe sepsis is defined as sepsis with evidence of organ dysfunction or tissue hypoperfusion 5, 6
• Septic shock is defined as sepsis with persistent hypotension requiring vasopressors to maintain MAP ≥65 mmHg and serum lactate >2 mmol/L despite adequate fluid resuscitation 6, 2

Special Considerations

• In neutropenic patients, white blood cell count cannot be used as a criterion to define sepsis 5, 6
• The SOFA score has demonstrated superior predictive validity for in-hospital mortality in ICU patients compared to SIRS criteria and qSOFA 7, 3
• For non-ICU patients, qSOFA has shown better predictive validity than SOFA for in-hospital mortality 3
• When SOFA score is >11, sensitivity and negative predictive values for sepsis diagnosis approach 100% 7

Monitoring and Re-evaluation

• Risk stratification should guide re-evaluation frequency: high-risk patients every 30 minutes, moderate-risk every hour, and low-risk every 4-6 hours 1
• Deterioration or lack of improvement should prompt immediate re-evaluation 1
• Regular assessment of vital signs, mental status, urine output, and peripheral perfusion is essential for monitoring sepsis progression 6

Pitfalls and Caveats

• The previous SIRS criteria (from 1992) are overly sensitive and non-specific, which may lead to overdiagnosis 5, 2
• The term "severe sepsis" is now considered redundant as sepsis itself implies organ dysfunction 2
• Different scoring systems have varying performance depending on the clinical setting (ICU vs. non-ICU) 3
• Delayed recognition of sepsis significantly increases mortality, emphasizing the importance of early screening with appropriate tools 4