How this instrument works
The check is deliberately narrow: suspected or confirmed infection, and a Sequential Organ Failure Assessment (SOFA) score that has risen by two points or more from the patient's baseline. Both boxes have to be checked for the result to read positive; either one alone returns negative, because Sepsis-3 defines sepsis as life-threatening organ dysfunction caused by a dysregulated response to infection — not infection by itself, however serious it looks, and not organ dysfunction from some unrelated cause.
Mervyn Singer, Clifford Deutschman, and the rest of the task force published this definition in 2016, deliberately retiring the older approach built around SIRS — systemic inflammatory response syndrome, a checklist of fever, fast heart rate, fast breathing, and abnormal white cell count. SIRS caught too many people: a straightforward flu or a routine post-operative fever meets two SIRS criteria without the patient being anywhere close to sepsis, so the older definition was flagging danger where often there was none. Requiring an actual jump in organ function, measured by SOFA, replaced that broad net with a sharper one.
This site's SOFA score calculator supplies the second half of the check here — it works out the organ dysfunction score from respiratory, cardiovascular, hepatic, coagulation, renal, and neurologic measurements, and comparing today's total against a documented baseline is what tells you whether it rose by two or more. A full SOFA calculation is not always available at the moment a patient first presents, which is precisely why a faster screening tool, qSOFA, exists for that earlier moment — three simple bedside signs meant to flag who might need the fuller SOFA workup in the first place, not to diagnose sepsis on its own.
- Set Suspected or confirmed infection to Yes if there is a clinical or microbiological reason to suspect one.
- Set SOFA score increased by ≥2 points from baseline to Yes only after calculating both scores — use this site's SOFA calculator if the current total isn't already known.
- Read the result: 1 means both Sepsis-3 criteria are met, 0 means at least one is missing.
Worked example — three combinations, one true positive
Suspected infection set to yes and a SOFA rise of 2 or more also set to yes: both conditions are satisfied, and the result reads 1 — this patient meets the Sepsis-3 definition. Change nothing about the infection but flip the SOFA rise to no, perhaps because today's organ-function score sits only 1 point above baseline, and the result flips to 0: an infection is present, but without the required 2-point organ-dysfunction rise, Sepsis-3 is not met.
Reverse it instead: no suspected infection, but a SOFA score that has risen by 2 points or more from baseline for some other reason — a new medication, an unrelated bleed, post-surgical organ strain — and the result again reads 0. Organ dysfunction without a suspected infectious trigger points toward a different workup entirely; the 1 result is reserved for the single combination where both conditions are true at once.
Questions
Why does Sepsis-3 require both infection and organ dysfunction?
Because infection alone is common and usually not life-threatening, while the organ dysfunction requirement is what distinguishes sepsis from an ordinary infection the body is handling well. The 2016 task force built the definition specifically to flag the smaller, more dangerous group — patients whose infection has triggered a response severe enough to be measurably harming the heart, lungs, kidneys, liver, blood clotting, or brain.
What replaced the older SIRS-based definition, and why?
Sepsis-3 replaced it, largely because SIRS criteria — fever, fast heart rate, fast breathing, abnormal white cell count — triggered on a huge share of hospitalised patients with nothing close to sepsis, including plenty recovering normally from surgery or a mild viral illness. Requiring a documented rise in SOFA score in addition to infection produces a smaller, more specific group genuinely at elevated risk of dying, which was the whole point of the 2016 revision.
Where does the SOFA score used here come from?
From this site's separate SOFA score calculator, which totals points across six organ systems — respiratory, cardiovascular, hepatic, coagulation, renal, and neurologic — from lab values and clinical measurements. Sepsis-3 needs the change in that total from a documented baseline, not just today's number in isolation, so both a current and a baseline SOFA calculation are needed before this checker's second input can be answered honestly.
What is qSOFA, and why isn't it used here?
Quick SOFA is a fast three-item bedside screen — low blood pressure, fast breathing, altered mental status — meant to flag, in seconds and without lab work, which patients with suspected infection might be sick enough to warrant a full SOFA calculation. It is a screening step toward this checker's second input, not a replacement for it; Sepsis-3 itself is defined using full SOFA, and qSOFA was validated as a predictor of outcome rather than as a diagnostic criterion.
Does a negative result here mean the patient is not seriously ill?
No — it only means the specific, literal Sepsis-3 combination is not met at this moment. A patient can be critically ill from an infection without yet showing a 2-point SOFA rise, or from organ dysfunction with no infectious cause identified yet; both situations need urgent clinical attention, they are just not classified as sepsis by this particular definition until the second criterion is documented.
Can this calculator diagnose sepsis by itself?
No. It performs exactly one logical check — infection present, and SOFA risen by 2 or more — and returns whether both are true. Confirming suspected infection and calculating an accurate SOFA change both require clinical judgment, laboratory data, and often imaging or cultures; this instrument only combines two answers a clinician has already worked out.
References
- Singer M et al. 2016, JAMA — Sepsis-3 consensus definitions (PubMed)
- Seymour CW et al. 2016, JAMA — Sepsis-3 clinical criteria assessment (PubMed)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.