Sepsis-3 Criteria Interpreter
Sepsis-3 Criteria Interpreter
Read the 2016 Sepsis-3 definitions: infection plus a SOFA rise of 2 or more is sepsis, and what has to be added to that before it is septic shock.
Sepsis-3 category
Criteria → Sepsis-3 categorySuspected infection, SOFA risen 4 points from baseline, noradrenaline running to hold a MAP of 65 mmHg, fluid resuscitation complete, lactate 3.4 mmol/L
The 2016 definitions
- Sepsis
- life-threatening organ dysfunction caused by a dysregulated host response to infection
- Organ dysfunction
- an acute change in total SOFA score of 2 points or more consequent to the infection
- Baseline SOFA
- assumed zero unless pre-existing organ dysfunction is documented
- Septic shock
- a subset of sepsis in which circulatory and cellular/metabolic abnormalities substantially increase mortality
- MAP target
- 65 mmHg or greater, maintained by vasopressor
- Lactate
- greater than 2 mmol/L (>18 mg/dL), in the absence of hypovolaemia
Worked example
Suspected infection, SOFA risen 4 points from baseline, noradrenaline running to hold a MAP of 65 mmHg, fluid resuscitation complete, lactate 3.4 mmol/L
Infection present, and the SOFA rise of 4 is ≥2 → sepsis
Vasopressor required for MAP ≥65 mmHg, after adequate fluids → first shock criterion met
Lactate 3.4 mmol/L is above 2 mmol/L → second shock criterion met
Both shock criteria met on a background of sepsis → septic shock
What Sepsis-3 changed in 2016
| Before 2016 | Under Sepsis-3 | Why |
|---|---|---|
| SIRS criteria defined sepsis | SIRS is not part of the definition | Two or more SIRS criteria were “unanimously considered by the task force to be unhelpful” — they are present in huge numbers of hospital inpatients who never become septic |
| Sepsis, severe sepsis, septic shock | Sepsis and septic shock only | Organ dysfunction moved into the definition of sepsis itself, so “under this terminology, ‘severe sepsis’ becomes superfluous” |
| Sepsis = infection + inflammation | Sepsis = infection + organ dysfunction | Inflammation is a normal and often protective response to infection; it is the organ dysfunction that makes the illness life-threatening |
| No single organ-dysfunction metric | An acute SOFA rise of ≥2 points | A rise of 2 carried roughly 10% hospital mortality in patients with presumed infection, which is the risk level the task force wanted the word to mean |
Which tool does which job
| Tool | Role under Sepsis-3 | Where it is on this site |
|---|---|---|
| SOFA | Defines organ dysfunction. Its rise of ≥2 points is the sepsis criterion | SOFA score calculator |
| qSOFA | Prognostic prompt in suspected infection. Not part of the definition and never intended as a screening test | qSOFA score calculator |
| Lactate | One of the two septic shock criteria, at a threshold of >2 mmol/L | lactate unit converter |
| Procalcitonin | No role in the definition at all; used for antibiotic stewardship | procalcitonin interpreter |
| Shock index | No role in the definition; catches compensated shock before the blood pressure falls | shock index calculator |
qSOFA was never a screening tool, and its own authors have said so
Sepsis-3 replaced a definition built on inflammation with one built on organ dysfunction. Sepsis is “life-threatening organ dysfunction caused by a dysregulated host response to infection”, and organ dysfunction is operationalised as an acute rise in the total SOFA score of 2 points or more, with the baseline assumed to be zero unless pre-existing dysfunction is documented. Septic shock is a subset of that: sepsis in which, after adequate fluid resuscitation, a vasopressor is needed to hold a mean arterial pressure of 65 mmHg or above and the serum lactate is above 2 mmol/L (18 mg/dL). The two thresholds were not chosen for elegance — a SOFA of 2 or more marked roughly 10% hospital mortality in patients with presumed infection, and the shock combination marked over 40%.
The single most common misuse of this framework is treating qSOFA as a sepsis screen. It is not one, and that is not an outside criticism: two members of the Sepsis-3 task force wrote an editorial saying so. “Crucially, qSOFA was never intended to be a ‘rule out’ screening tool,” they wrote, and “qSOFA was developed in symptomatic patients, thus it is not a screening tool for ‘sepsis’.” The task force “recognized it would offer specificity rather than sensitivity” — and the published sensitivities bear that out, ranging across studies from 0.12 to 0.98. A qSOFA of 0 or 1 in a patient you are worried about tells you almost nothing. The qSOFA page carries the same warning from the guideline side.
Two things Sepsis-3 deliberately deleted are still in daily use and still cause confusion. The first is SIRS, whose use inside the definition “was abandoned” — not because inflammation is irrelevant but because two SIRS criteria are met by an enormous number of hospital inpatients who are never septic, so the criteria cannot discriminate. The second is “severe sepsis”, which vanished as a category: once organ dysfunction is part of the definition of sepsis, severe sepsis is just sepsis. Coding systems, trial protocols and local guidelines written before 2016 still use both terms, so a chart that says “severe sepsis” is telling you about the vintage of the document rather than about the patient.
Finally, a caution about the arithmetic this page performs. It reads criteria; it does not measure anything. The SOFA delta you enter is only as good as the baseline you subtracted, and in a patient with chronic renal or liver disease the baseline is not zero. Score the components on the SOFA page rather than estimating them, and remember that the cardiovascular and neurological components need bedside assessment and cannot be filled in from a laboratory report.
Frequently asked questions
What is the definition of sepsis under Sepsis-3?
Life-threatening organ dysfunction caused by a dysregulated host response to infection — in practice, suspected or confirmed infection plus an acute rise in the total SOFA score of 2 points or more from baseline.
What lactate level and MAP define septic shock?
Singer et al specify a vasopressor requirement to maintain a mean arterial pressure of 65 mmHg or greater together with a serum lactate above 2 mmol/L (18 mg/dL), both persisting despite adequate fluid resuscitation. Both are required, not either.
Is qSOFA a screening tool for sepsis?
No. Two authors of Sepsis-3 wrote that “qSOFA was never intended to be a ‘rule out’ screening tool” and that because it was developed in symptomatic patients, “it is not a screening tool for ‘sepsis'”. It was designed to offer specificity rather than sensitivity in patients in whom infection is already suspected.
Why did Sepsis-3 drop SIRS and severe sepsis?
The task force judged two or more SIRS criteria “unhelpful” for defining sepsis, because they are met by very large numbers of inpatients who never develop sepsis. And once organ dysfunction became part of the definition of sepsis itself, “severe sepsis” was redundant — in the paper’s words, it “becomes superfluous”.
What mortality figures was the definition derived against?
A SOFA score of 2 or more carried “an overall mortality risk of approximately 10% in a general hospital population with presumed infection”, and the septic shock criteria carried “hospital mortality rates greater than 40%”. Both figures are from Singer et al, JAMA 2016;315(8):801–10.
Related calculators
References
- Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801–10.
- Singer M, Shankar-Hari M. qSOFA, cue confusion. Ann Intern Med. 2018. doi:10.7326/M17-3415 (PMID 29404580).
- Seymour CW, Liu VX, Iwashyna TJ, et al. Assessment of clinical criteria for sepsis: for the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):762–74.
- Shankar-Hari M, Phillips GS, Levy ML, et al. Developing a new definition and assessing new clinical criteria for septic shock: for the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):775–87.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.