Sepsis Calculator - Sepsis-3 Criteria (qSOFA + SOFA)
This calculator applies the Sepsis-3 consensus criteria published in JAMA 2016. First calculate the bedside qSOFA screen (three clinical observations, no lab work needed). Then, if infection is suspected and qSOFA is 2 or more, complete the full SOFA score to assess organ dysfunction across six systems. The calculator also checks whether septic shock criteria are met. Results update instantly as you enter values.
Formula
Worked example
A patient with suspected pneumonia has: GCS 14 (altered), RR 24 breaths/min, SBP 95 mmHg. qSOFA = 1 (AMS) + 1 (RR >= 22) + 1 (SBP <= 100) = 3/3, positive. Full SOFA: PaO2/FiO2 280 = 2 pts; platelets 90 = 2 pts; GCS 14 = 1 pt; MAP 68 without vasopressors = 1 pt; bilirubin 0.9 = 0 pts; creatinine 1.5 = 1 pt. SOFA total = 7/24. An acute SOFA increase >= 2 from baseline meets the sepsis criteria. Lactate 2.8 mmol/L without vasopressor = septic shock not yet met (would need vasopressor to be added).
What are the Sepsis-3 Criteria?
The Sepsis-3 definition, published in JAMA in February 2016 by a 19-member task force of the Society of Critical Care Medicine and the European Society of Intensive Care Medicine, replaced the older SIRS-based definitions. Sepsis-3 defines sepsis as "life-threatening organ dysfunction caused by a dysregulated host response to infection." Organ dysfunction is identified by an acute increase of 2 or more points in the Sequential Organ Failure Assessment (SOFA) score from the patient's baseline, which represents an estimated in-hospital mortality greater than 10%. The definition removed the older "severe sepsis" category and redefined septic shock as a subset of sepsis with vasopressor requirement to maintain MAP >= 65 mmHg plus lactate > 2 mmol/L despite adequate fluid resuscitation, carrying mortality above 40%.
qSOFA: The Bedside Screen
The Quick SOFA (qSOFA) score was introduced alongside Sepsis-3 as a simple bedside tool that requires no blood tests. It assigns one point each for: altered mental status (any GCS below 15), respiratory rate 22 or more breaths per minute, and systolic blood pressure 100 mmHg or below. A score of 2 or 3 is considered positive and is associated with a 3- to 14-fold increase in in-hospital mortality in patients with suspected infection outside the ICU. A positive qSOFA should prompt clinical reassessment and immediate SOFA scoring. Importantly, qSOFA is a screening tool, not a diagnostic criterion. A negative qSOFA does not rule out sepsis if there is strong clinical concern. Some updated guidelines, including the Surviving Sepsis Campaign 2021, note that qSOFA alone has lower sensitivity than SOFA for sepsis identification and should not be used as a standalone test.
SOFA Score: Assessing Organ Dysfunction Across Six Systems
The full SOFA score quantifies organ dysfunction in six systems, each scored 0-4 for a maximum of 24 points. Respiratory: PaO2/FiO2 ratio (lower ratios score higher; ventilation affects scoring below 200). Coagulation: platelet count (below 150 x10^3/uL begins scoring). Neurological: Glasgow Coma Scale total (below 15 scores 1 point, below 6 scores 4). Cardiovascular: MAP below 70 mmHg or vasopressor requirement (higher doses score more). Hepatic: total bilirubin (above 1.2 mg/dL begins scoring). Renal: serum creatinine (above 1.2 mg/dL begins scoring) or urine output below 500 mL/day. Use the most abnormal value for each parameter over a 24-hour period. The clinically important threshold for the Sepsis-3 definition is an acute increase of 2 or more from the patient's known or presumed baseline (0 if no chronic organ dysfunction is known).
Septic Shock: Identifying the Highest-Risk Patients
Septic shock under Sepsis-3 requires three simultaneous conditions: (1) the underlying sepsis diagnosis (suspected infection + organ dysfunction), (2) a vasopressor requirement to maintain MAP >= 65 mmHg despite adequate volume resuscitation, and (3) serum lactate above 2 mmol/L. The lactate criterion captures circulatory, cellular, and metabolic abnormalities beyond hypotension alone. Hospital mortality in septic shock exceeds 40% in published cohort data. Elevated lactate without hypotension (cryptic shock, or "occult" shock) also warrants urgent resuscitation because lactate > 2 mmol/L is independently associated with mortality. The Surviving Sepsis Campaign bundles recommend measuring lactate, drawing blood cultures, starting antibiotics, and giving 30 mL/kg IV crystalloid within specific time windows.
SOFA Score and Estimated ICU Mortality
| SOFA Score | Estimated Mortality | Risk Level |
|---|---|---|
| 0-1 | < 10% | Low |
| 2-3 | ~ 10% | Low-Moderate |
| 4-5 | ~ 15% | Moderate |
| 6-7 | ~ 20% | Moderate-High |
| 8-9 | ~ 30% | High |
| 10-11 | ~ 40% | High |
| 12-14 | ~ 50% | Very High |
| >= 15 | > 80% | Critical |
Approximate in-hospital mortality rates by total SOFA score, based on the original Singer et al. 2016 validation data. An acute increase >= 2 from baseline = sepsis criterion met.
Frequently asked questions
What is the difference between sepsis and septic shock under Sepsis-3?
Sepsis (Sepsis-3) is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute SOFA increase of 2 or more from baseline in a patient with suspected or confirmed infection. Septic shock is a subset of sepsis in which circulatory and cellular/metabolic abnormalities are so severe that vasopressors are needed to maintain MAP >= 65 mmHg and serum lactate is above 2 mmol/L despite adequate fluid resuscitation. Septic shock carries substantially higher mortality (> 40%) than sepsis without shock.
Can I use qSOFA alone to diagnose or rule out sepsis?
No. qSOFA is a screening tool designed to identify patients at high risk of poor outcomes from infection outside the ICU - it predicts mortality, not sepsis. A positive qSOFA (score >= 2) should prompt full SOFA assessment, blood cultures, and clinical evaluation, but does not by itself confirm sepsis. A negative qSOFA does not rule out sepsis; if there is strong clinical concern, full SOFA and laboratory workup should still be performed. The Surviving Sepsis Campaign 2021 guidelines explicitly state that qSOFA should not be used as a single screening tool for sepsis.
What is a "normal" SOFA score and what counts as an acute change?
In patients without pre-existing organ dysfunction, the baseline SOFA score is assumed to be 0. An acute increase of 2 or more points above this baseline in the presence of suspected infection satisfies the organ dysfunction criterion for sepsis. In patients with known chronic organ disease (for example, chronic liver disease causing elevated bilirubin), the baseline may be above 0, and the relevant threshold is a 2-point rise above that individual baseline, not above zero.
How is PaO2/FiO2 ratio calculated and what does it mean?
PaO2/FiO2 (the P/F ratio) divides the arterial partial pressure of oxygen in mmHg by the fraction of inspired oxygen as a decimal (for example, room air FiO2 is 0.21, so a PaO2 of 80 mmHg on room air gives P/F = 80 / 0.21 = 381). A normal P/F ratio is approximately 400-500 mmHg. The SOFA scale scores 0 for >= 400, 1 for 300-399, and increases to 4 for below 100 on mechanical ventilation. P/F below 300 indicates impaired oxygenation, and below 200 on ventilation meets the ARDS Berlin definition threshold.
Does this calculator replace clinical judgment?
No. SOFA and qSOFA are evidence-based clinical decision-support tools, but the Sepsis-3 diagnosis requires clinical interpretation by a qualified healthcare professional. The tools do not account for the clinical probability of infection, the trajectory of the patient over time, or the cause of organ dysfunction (which may be non-infectious). Treatment decisions, antibiotic selection, and resuscitation strategy should always be made by clinicians integrating the full clinical picture, local microbiology patterns, and patient values.