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, diagnosed by the presence of documented or suspected infection plus specific clinical criteria indicating systemic inflammatory response and organ dysfunction. 1, 2

Diagnostic Framework for Sepsis

1. Sepsis Definition and Criteria

According to the Surviving Sepsis Campaign guidelines, sepsis can be diagnosed when a patient has:

• Documented or suspected infection PLUS
• Signs of systemic inflammatory response, including: 1

General Variables:

• Fever (>38.3°C)
• Hypothermia (core temperature <36°C)
• Heart rate >90/min or >2 SD above normal value for age
• Tachypnea
• Altered mental status
• Significant edema or positive fluid balance (>20 mL/kg over 24 hrs)
• Hyperglycemia (plasma glucose >140 mg/dL) in the absence of diabetes

Inflammatory Variables:

• Leukocytosis (WBC count >12,000/μL)
• Leukopenia (WBC count <4,000/μL)
• Normal WBC count with >10% immature forms
• Plasma C-reactive protein >2 SD above normal value
• Plasma procalcitonin >2 SD above normal value

Hemodynamic Variables:

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

Organ Dysfunction Variables:

• Arterial hypoxemia (PaO₂/FiO₂ <300)
• Acute oliguria (urine output <0.5 mL/kg/hr for at least 2 hrs despite adequate fluid)
• Creatinine increase >0.5 mg/dL
• Coagulation abnormalities (INR >1.5 or aPTT >60 sec)
• Ileus (absent bowel sounds)
• Thrombocytopenia (platelet count <100,000/μL)
• Hyperbilirubinemia (plasma total bilirubin >4 mg/dL)

Tissue Perfusion Variables:

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

2. Severe Sepsis Criteria

Severe sepsis is defined as sepsis plus sepsis-induced tissue hypoperfusion or organ dysfunction, indicated by any of the following: 1

• Sepsis-induced hypotension
• Lactate above upper limits of laboratory normal
• Urine output <0.5 mL/kg/hr for >2 hours despite adequate fluid resuscitation
• Acute lung injury with PaO₂/FiO₂ <250 in the absence of pneumonia as infection source
• Acute lung injury with PaO₂/FiO₂ <200 in the presence of pneumonia as infection source
• Creatinine >2.0 mg/dL
• Bilirubin >2 mg/dL
• Platelet count <100,000/μL
• Coagulopathy (INR >1.5)

3. Septic Shock Criteria

Septic shock is defined as: 1

• Severe sepsis with hypotension persistent despite adequate fluid resuscitation
• Requiring vasopressors to maintain MAP ≥65 mmHg
• Serum lactate >2 mmol/L (in newer definitions) 2

Updated Sepsis-3 Criteria (2016)

The more recent Sepsis-3 definitions have updated the diagnostic approach: 2

• Sepsis: Life-threatening organ dysfunction caused by a dysregulated host response to infection

  • Clinically identified by an increase in Sequential Organ Failure Assessment (SOFA) score ≥2 points

• Septic Shock: A subset of sepsis with profound circulatory, cellular, and metabolic abnormalities

  • Clinically identified by vasopressor requirement to maintain MAP ≥65 mmHg AND
  • Serum lactate >2 mmol/L despite adequate volume resuscitation

• Quick SOFA (qSOFA) for rapid bedside assessment:

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

Special Considerations

Pediatric Sepsis Criteria

Diagnostic criteria for sepsis in pediatric patients include: 1

• Signs and symptoms of inflammation plus infection
• Hyper- or hypothermia (rectal temperature >38.5°C or <35°C)
• Tachycardia (may be absent in hypothermic patients)
• At least one indicator of altered organ function:
  • Altered mental status
  • Hypoxemia
  • Increased serum lactate
  • Bounding pulses

Neutropenic Patients

In neutropenic patients: 1

• WBC count cannot be used as a criterion to define sepsis
• Other criteria remain applicable
• Special attention to inflammatory markers like C-reactive protein and procalcitonin

Clinical Pearls and Pitfalls

• Early recognition is critical: Systemic symptoms like altered mental status, dyspnea, gastrointestinal symptoms, and muscle weakness are strong predictors of severe sepsis development 3

• Heterogeneous presentation: The clinical presentation of sepsis is highly variable, with symptoms typically peaking 1-2 days before hospital presentation 4

• Fever is not universal: Fever is present in only a minority of sepsis patients and its absence should not rule out sepsis 4

• Rapid progression: The transition from infection to sepsis can occur rapidly, emphasizing the need for vigilant monitoring of at-risk patients 3

• Mortality correlation: Signs of neurologic dysfunction, significant respiratory conditions, and hypotension are strongly associated with sepsis diagnosis, hospital mortality, and ICU admission 4