Sepsis screening tools explained: SIRS, qSOFA, SOFA and what the guidelines say

The definitions

In 2016 a task force convened by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine published the Third International Consensus Definitions, known as Sepsis-3 (Singer and colleagues, JAMA). They defined sepsis as life-threatening organ dysfunction caused by a dysregulated host response to infection, and treated the older term “severe sepsis” as redundant. Septic shock is a subset in which circulatory and metabolic abnormalities are profound enough to raise mortality, defined in that paper by the need for vasopressors to keep mean arterial pressure at 65 mmHg or above and a lactate above 2 mmol/L despite adequate fluid.

This is exam-preparation revision, not clinical guidance. In practice, follow your own organisation’s policies and current guidelines.

SIRS

The systemic inflammatory response syndrome criteria predate Sepsis-3. A patient meets SIRS if two or more of these are present.

• Temperature above 38 degrees Celsius or below 36.
• Heart rate above 90 beats per minute.
• Respiratory rate above 20 breaths per minute, or a low arterial carbon dioxide.
• White cell count above 12,000 or below 4,000 per microlitre, or more than 10 percent immature forms.

qSOFA

The quick SOFA score is a bedside prompt introduced with Sepsis-3 for patients outside intensive care who have suspected infection. It scores one point for each of: respiratory rate of 22 or more per minute, altered mental status, and systolic blood pressure of 100 mmHg or less. A score of two or more suggests a greater risk of a poor outcome and should prompt further assessment. It is a prompt to think, not a diagnostic test, and not part of the definition of sepsis.

SOFA

The Sequential Organ Failure Assessment score grades dysfunction in six systems: respiratory, coagulation, liver, cardiovascular, central nervous system and renal. An acute rise of two points or more from baseline indicates organ dysfunction in the Sepsis-3 framework. For exams, you rarely need to calculate a whole score, but you should know what it measures: organ function, not the presence of inflammation.

What the 2021 Surviving Sepsis guidance says

The 2021 Surviving Sepsis Campaign guidelines (Evans and colleagues) contain several recommendations that are often tested at exam level. Treat the following as a summary and read the guideline for exact wording.

• For adults with possible septic shock or a high likelihood of sepsis, give antimicrobials immediately, ideally within one hour of recognition.
• For adults with possible sepsis without shock, assess quickly whether infection is likely, and give antimicrobials within three hours if concern persists.
• Measure blood lactate in adults with suspected sepsis.
• For sepsis-induced hypoperfusion or septic shock, the guideline suggests at least 30 mL per kg of intravenous crystalloid within the first three hours.
• For adults on vasopressors, aim for an initial mean arterial pressure target of 65 mmHg.
• The guideline recommends against using qSOFA alone, compared with SIRS, NEWS or MEWS, as a single screening tool for sepsis or septic shock.

How this appears in exam questions

A typical question describes a patient with a fever, a high heart rate and a high respiratory rate, perhaps with confusion and low blood pressure, and asks for the first action or the best next step. Safe ordering usually involves recognising the picture, escalating, getting access, taking cultures where this does not delay antibiotics, giving timely antimicrobials, fluids and monitoring. Do not memorise a rigid sequence from one hospital protocol. Use the principle: early recognition and early treatment, with reassessment.

A worked example: reading a patient against the tools

An invented case. A 68-year-old man arrives with a cough, a temperature of 38.6 degrees, a heart rate of 112, a respiratory rate of 24 and a blood pressure of 96 over 58. He is a little drowsy. Check SIRS: temperature, heart rate and respiratory rate are all abnormal, so he meets at least two SIRS criteria. Check qSOFA: respiratory rate 22 or more, altered mentation and systolic pressure 100 or less are all present, so the score is three. He is high risk and needs immediate escalation, with assessment for organ dysfunction and early antimicrobials once sepsis is suspected, in line with local protocol and the guideline timings.

Notice what the tools do and do not do. They flag risk. The decision to treat comes from clinical judgment and local pathways.

Pitfalls in questions

Typical errors include treating qSOFA as a diagnosis, forgetting that a normal temperature does not exclude sepsis, especially in older patients, children and those on immunosuppressants, and waiting for blood results before treating a patient who looks very unwell. Another is confusing the terms: SIRS is a response, sepsis needs organ dysfunction in the Sepsis-3 framework and septic shock needs vasopressors and a raised lactate despite fluids. Read the stem for the patient’s state and for what it asks you to do first.

Children and pregnancy

The adult criteria do not apply directly to children, for whom age-specific vital sign ranges and paediatric sepsis tools are used, and pregnancy changes normal ranges and the presentation of illness. If an exam question is about a child or a pregnant woman, expect it to use the relevant specialty approach, and recall that a deteriorating child or a pregnant woman with suspected infection is also an emergency to escalate early.

Early warning scores

Many health systems use aggregate early warning scores, such as the National Early Warning Score, which combine observations such as respiratory rate, oxygen saturation, blood pressure, pulse, temperature and level of consciousness into a single score that triggers a graded response. They are designed to spot general deterioration, not sepsis specifically, but they are useful in sepsis recognition. The 2021 guideline lists NEWS and MEWS among the tools it compares with qSOFA. For an exam, know that such scores exist, that a rising score means increasing concern, and that the response is tied to the score according to local policy.

A stepwise approach for exam stems

Use a short sequence when a stem describes a possible sepsis case. First, recognise: look for infection plus signs of deterioration. Second, call for help and escalate. Third, assess airway, breathing and circulation and give oxygen where needed. Fourth, obtain access and send blood tests, including cultures and lactate, without delaying antimicrobials. Fifth, give antimicrobials in the guideline time frame and fluids where indicated. Sixth, monitor closely and reassess. The order may vary with the stem, but the idea of early recognition, early treatment and frequent reassessment is constant.

The short version

Sepsis is life-threatening organ dysfunction caused by a dysregulated response to infection. SIRS flags inflammation, qSOFA is a prompt for further assessment, SOFA measures organ dysfunction and early warning scores track general deterioration. The 2021 guidance stresses early recognition, timely antimicrobials, fluids where indicated and reassessment. In exams, choose the answer that recognises the picture and escalates early. The DHA exam for nurses and for doctors pages show how emergency care fits into each role’s preparation.

Cautions

Definitions have changed over time and tools differ between countries. Early warning scores such as NEWS2 are used in many health systems and have their own thresholds. Know which tools your syllabus emphasises. For related revision, see the sepsis and the deteriorating patient guide, the SBAR post for escalation, and practice questions on emergencies.

Related guide

For the bedside signs and the first hour in plain steps, see sepsis and the deteriorating patient.

Frequently asked questions