What are the clinical parameters to diagnose sepsis?

Clinical Parameters to Diagnose Sepsis

Use the NEWS2 scoring system combined with suspected or confirmed infection as the primary clinical tool to diagnose and risk-stratify sepsis in patients aged 16 and over. 1

Core Diagnostic Framework

The diagnosis of sepsis requires two essential components: evidence of infection AND evidence of organ dysfunction or systemic inflammatory response. 2

NEWS2 Scoring System (Primary Tool)

The NEWS2 score incorporates six physiological parameters, each scored to create an aggregate that determines sepsis risk: 1

Physiological Parameters Measured:

• Respiratory rate: Abnormal if <8 or >25 breaths/minute 1
• Oxygen saturation (SpO₂): Concerning if <95% on room air 1
• Supplemental oxygen requirement: Any oxygen use scores points 1
• Systolic blood pressure: Hypotension defined as <90 mmHg 1
• Heart rate: Abnormal if <40 or >130 beats/minute 1
• Level of consciousness: Using CVPU scale (Confusion-new, Voice response, Pain response, Unresponsive) 1
• Temperature: Fever >39.1°C or hypothermia <35.0°C 1

Risk Stratification Based on NEWS2 Score: 1

• Score ≥7: High risk of severe illness or death from sepsis
• Score 5-6: Moderate risk of severe illness or death from sepsis
• Score 1-4: Low risk of severe illness or death from sepsis
• Score 0: Very low risk of severe illness or death from sepsis
• Score of 3 in any single parameter: May indicate increased sepsis risk regardless of total score

Critical Clinical Signs That Override NEWS2 Score

Immediately evaluate for high sepsis risk if ANY of the following are present, regardless of NEWS2 score: 1

• Mottled or ashen skin appearance
• Non-blanching petechial or purpuric rash
• Cyanosis of skin, lips, or tongue

Additional Diagnostic Criteria from Society of Critical Care Medicine

Systemic Inflammatory Response Indicators: 2

• Temperature: Core temperature >38.3°C or <36°C 2
• Heart rate: >90 beats/minute or >2 SD above normal for age 2
• Respiratory rate: >20 breaths/minute 2
• White blood cell count: >12,000/μL, <4,000/μL, or >10% immature forms 2

Organ Dysfunction Markers: 2

• Cardiovascular: SBP <90 mmHg, MAP <70 mmHg, or SBP decrease >40 mmHg 2
• Renal: Urine output <0.5 mL/kg/h for ≥2 hours despite adequate fluid resuscitation, or creatinine increase ≥0.5 mg/dL 2
• Respiratory: PaO₂/FiO₂ <300 2
• Hematologic: Platelet count <100,000/μL, INR >1.5, or aPTT >60 seconds 2
• Hepatic: Total bilirubin >4 mg/dL 2
• Metabolic: Lactate >1 mmol/L 2
• Perfusion: Decreased capillary refill, skin mottling, or peripheral cyanosis 2

Laboratory Investigations

Essential Initial Tests

Blood Cultures: 1

• Obtain at least 2 sets (aerobic and anaerobic) before antibiotics when sepsis is suspected 2
• Specific indications include: fever, chills, hypothermia, leukocytosis, left-shift neutrophils, neutropenia, hypoalbuminemia, new renal failure, or hemodynamic compromise 1
• Draw as soon as possible after fever onset (bacteria clear rapidly from blood) 1

Lactate Measurement: 2

• Elevated lactate >1 mmol/L indicates tissue hypoperfusion 2
• Serial measurements guide resuscitation effectiveness 2

Biomarkers (Adjunctive, Not Diagnostic Alone)

Procalcitonin (PCT): 1

• Levels ≥1.5 ng/mL have 100% sensitivity and 72% specificity for sepsis in ICU patients 1
• Rises more quickly than CRP and correlates more closely with sepsis severity 1
• Cannot differentiate sepsis from SIRS alone; must be part of systematic evaluation 1

C-Reactive Protein (CRP): 1

• Levels ≥50 mg/L have 98.5% sensitivity and 75% specificity for probable/definite sepsis 1
• Less specific than PCT but widely available 1

Important Caveat: Sequential daily measurements of inflammatory markers are more valuable than single measurements. 1

Monitoring Frequency Based on Risk Level

Re-calculate NEWS2 score at these intervals: 1

• High risk (score ≥7): Every 30 minutes
• Moderate risk (score 5-6): Every hour
• Low risk (score 1-4): Every 4-6 hours
• Very low risk (score 0): Per routine protocol

Key Clinical Pitfalls

Always interpret NEWS2 in context of: 1

• Patient's baseline physiology and comorbidities
• Clinical trajectory (deteriorating vs. improving)
• Response to interventions

Recognize that NEWS2 may underestimate risk when: 1

• Condition is deteriorating despite interventions
• Patient has not improved since previous assessment
• Certain high-risk clinical signs are present (mottled skin, purpuric rash, cyanosis)

In neutropenic patients: White blood cell count cannot be used as a sepsis criterion. 2