Sepsis diagnostic criteria

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Parth Vikram Singh, MBBS[3] Jason Le, B.S.[4]

Synonyms and keywords: sepsis; septic shock; Sepsis-3; Phoenix Sepsis Score; SOFA; qSOFA

Diagnostic criteria

General principles

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. In adults, the Sepsis-3 operational definition identifies organ dysfunction as an acute increase in the Sequential Organ Failure Assessment (SOFA) score of ≥2 points attributable to infection.

A SOFA increase of ≥2 is an operational definition rather than a standalone etiologic test. Clinical assessment remains necessary to establish that infection is suspected or documented and to interpret organ dysfunction in context.

A SOFA increase of ≥2 in a patient with suspected infection is associated with in-hospital mortality of approximately 10%; septic shock, so defined, carries hospital mortality exceeding 40%. The 2016 criteria also lowered the septic-shock lactate threshold from >4 mmol/L to >2 mmol/L.

No diagnostic test or operational criterion provides a true gold standard for sepsis; contemporary definitions are validated primarily against clinically important outcomes, particularly mortality and organ dysfunction. Sepsis criteria therefore function as operational definitions rather than etiologic tests.

Adult Sepsis-3 criteria

Sepsis is suspected or documented infection accompanied by an acute increase in SOFA score of ≥2 points attributable to infection.

Septic shock is a subset of sepsis in which, despite adequate fluid resuscitation, vasopressors are required to maintain a mean arterial pressure of ≥65 mm Hg and serum lactate is >2 mmol/L (>18 mg/dL).

The septic-shock definition should not be applied on the basis of hypotension or lactate elevation alone; both vasopressor-dependent hypotension and lactate >2 mmol/L after adequate resuscitation are required.

SOFA score

The original SOFA score assigns 0-4 points in each of six organ systems. In the Sepsis-3 framework, an acute increase of ≥2 points attributable to infection operationalizes organ dysfunction.

System	0 points	1 point	2 points	3 points	4 points
Respiratory	PaO2/FiO2 ≥400	PaO2/FiO2 <400	PaO2/FiO2 <300	PaO2/FiO2 <200 with respiratory support	PaO2/FiO2 <100 with respiratory support
Coagulation	Platelets ≥150 ×103/μL	Platelets <150 ×103/μL	Platelets <100 ×103/μL	Platelets <50 ×103/μL	Platelets <20 ×103/μL
Liver	Bilirubin <1.2 mg/dL	Bilirubin 1.2-1.9 mg/dL	Bilirubin 2.0-5.9 mg/dL	Bilirubin 6.0-11.9 mg/dL	Bilirubin ≥12.0 mg/dL
Cardiovascular	MAP ≥70 mm Hg	MAP <70 mm Hg	Dopamine <5 μg/kg/min or dobutamine at any dose	Dopamine 5-15 μg/kg/min or epinephrine ≤0.1 μg/kg/min or norepinephrine ≤0.1 μg/kg/min	Dopamine >15 μg/kg/min or epinephrine >0.1 μg/kg/min or norepinephrine >0.1 μg/kg/min
Central nervous system	GCS 15	GCS 13-14	GCS 10-12	GCS 6-9	GCS <6
Renal	Creatinine <1.2 mg/dL	Creatinine 1.2-1.9 mg/dL	Creatinine 2.0-3.4 mg/dL	Creatinine 3.5-4.9 mg/dL or urine output <500 mL/day	Creatinine ≥5.0 mg/dL or urine output <200 mL/day

The SOFA score is a diagnostic operationalization of organ dysfunction and should not be interpreted as a substitute for clinical assessment of infection.

SOFA-2

SOFA-2 is a contemporary revision of the original SOFA score intended to improve applicability to current critical care practice. The most notable revisions involve the respiratory, cardiovascular, and kidney domains, including incorporation of SpO₂/FiO₂ and non-invasive ventilation in the respiratory domain and weight-standardized urine output in the kidney domain.

The most notable revisions in SOFA-2 are to the respiratory (SpO₂/FiO₂ and non-invasive ventilation), cardiovascular, and kidney (weight-standardized urine output) domains. Early multicenter data suggest SOFA-2 can alter sepsis case detection and prognostic classification, but the Sepsis-3 operational definition remains based on the original SOFA framework.

Pediatric sepsis: Phoenix criteria

The Phoenix Sepsis Score is the current international consensus framework for identifying pediatric sepsis. In children with suspected or confirmed infection, a Phoenix Sepsis Score of ≥2 points identifies sepsis. Septic shock is defined as sepsis with ≥1 cardiovascular point.

The Phoenix score incorporates respiratory, cardiovascular, coagulation, and neurologic dysfunction. It does not require SIRS and does not use the term "severe sepsis." In the validation cohort, Phoenix-defined sepsis was associated with in-hospital mortality of 7.1% in higher-resource settings and 28.5% in lower-resource settings; Phoenix-defined septic shock was associated with mortality of 10.8% and 33.5%, respectively.

Phoenix Sepsis Score

Domain	0 points	1 point	2 points	3 points
Respiratory 0-3 points	PaO2/FiO2 ≥400 or SpO2/FiO2 ≥292	PaO2/FiO2 <400 on any respiratory support or SpO2/FiO2 <292 on any respiratory support	PaO2/FiO2 100-200 and invasive mechanical ventilation (IMV), or SpO2/FiO2 148-220 and IMV	PaO2/FiO2 <100 and IMV, or SpO2/FiO2 <148 and IMV
Cardiovascular 0-6 points	No vasoactive medication; lactate <5 mmol/L; age-specific MAP above threshold	1 point each for 1 vasoactive medication, lactate 5-10.9 mmol/L, or age-specific MAP in the intermediate range	2 points each for ≥2 vasoactive medications, lactate ≥11 mmol/L, or age-specific MAP below threshold	—
Coagulation 0-2 points	Platelets ≥100 ×103/μL; INR ≤1.3; D-dimer ≤2 mg/L FEU; fibrinogen ≥100 mg/dL	1 point each for platelets <100 ×103/μL, INR >1.3, D-dimer >2 mg/L FEU, or fibrinogen <100 mg/dL; maximum 2 points	—	—
Neurologic 0-2 points	GCS >10 and pupils reactive	GCS ≤10	Fixed pupils bilaterally	—

For the cardiovascular component, age-specific mean arterial pressure thresholds are:

Age	0 points	1 point	2 points
<1 month	>30 mm Hg	17-30 mm Hg	<17 mm Hg
1-11 months	>38 mm Hg	25-38 mm Hg	<25 mm Hg
1 to <2 years	>43 mm Hg	31-43 mm Hg	<31 mm Hg
2 to <5 years	>44 mm Hg	32-44 mm Hg	<32 mm Hg
5 to <12 years	>48 mm Hg	36-48 mm Hg	<36 mm Hg
12-17 years	>51 mm Hg	38-51 mm Hg	<38 mm Hg

Pediatric sepsis: suspected or confirmed infection plus Phoenix Sepsis Score ≥2.

Pediatric septic shock: pediatric sepsis plus ≥1 cardiovascular point.

Screening and qSOFA

Screening tools are not diagnostic criteria. They are intended to identify patients who require further clinical assessment for possible sepsis and organ dysfunction.

For acutely ill hospitalized adults, the 2026 Surviving Sepsis Campaign recommends using NEWS, NEWS2, MEWS, or SIRS over qSOFA as a single screening tool (strong recommendation, moderate-certainty evidence). A positive qSOFA should still prompt evaluation for sepsis, and electronic qSOFA-triggered alerting has improved 90-day in-hospital mortality in a stepped-wedge trial; its low sensitivity, however, precludes its use as a sole screen.

qSOFA (≥2 of: respiratory rate ≥22/min, altered mentation [GCS <15], systolic blood pressure ≤100 mm Hg) is a bedside prognostic prompt rather than a diagnostic definition of sepsis.

The 2021 Surviving Sepsis Campaign recommended against qSOFA as a single screening tool, and the 2026 guideline retains this position while emphasizing that qSOFA may still be useful for detecting clinical deterioration and prompting further evaluation.

Other diagnostic approaches

No single biomarker, laboratory value, imaging study, screening score, or electronic health-record algorithm establishes sepsis. Lactate is useful for risk assessment and is part of the adult septic-shock definition, but an elevated lactate alone does not diagnose sepsis or septic shock. Biomarkers such as procalcitonin, C-reactive protein, and other inflammatory markers are adjunctive and should not replace clinical assessment.

The detailed use of lactate, cultures, inflammatory biomarkers, organ-function tests, and microbiologic diagnostics is addressed in Sepsis laboratory findings. Screening implementation and electronic-alert strategies are addressed in Sepsis screening.

Large-scale case identification

Administrative codes, electronic health-record algorithms, automated sepsis alerts, and other large-scale case-identification methods can support surveillance, quality improvement, and early recognition but should not be equated with the clinical diagnostic criteria for sepsis. Differences in case definitions and coding strategies can substantially alter reported incidence and mortality. Detailed epidemiologic and coding implications are addressed in Sepsis epidemiology.

Lactate and biomarkers

Serum lactate is incorporated into the adult septic-shock definition but is not independently diagnostic of sepsis. Lactate elevation may occur in sepsis for multiple reasons and should be interpreted in the clinical context.

Inflammatory and infection-related biomarkers may provide diagnostic or prognostic information, but no currently established biomarker replaces clinical assessment or the operational organ-dysfunction criteria. Detailed laboratory interpretation belongs in Sepsis laboratory findings.