Sepsis Screening: qSOFA vs SOFA vs NEWS2 vs SIRS

Sepsis is time-critical, and recognising it early changes outcomes. It is also a topic where scores get confused constantly: SIRS, qSOFA, SOFA, NEWS2, MEWS and, since 2025, SOFA-2. Which one is for what?

The one-line answer: SOFA defines organ dysfunction, qSOFA flags patients at risk of a poor outcome, and early warning scores such as NEWS2 screen. This article explains the difference and summarises what the Surviving Sepsis Campaign (SSC) 2021 and the 2025 German S3 sepsis guideline recommend.

Sepsis-3 in brief

The Sepsis-3 definitions (2016) are the international reference [1]:

• Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection.
• Organ dysfunction is operationalised as an acute increase in SOFA score of ≥2 points, associated with in-hospital mortality above 10%.
• Septic shock is sepsis requiring vasopressors to maintain a mean arterial pressure ≥65 mmHg and with serum lactate >2 mmol/L despite adequate fluid resuscitation. Hospital mortality exceeds 40%.
• "Severe sepsis" was dropped as redundant.

For exams, note that SIRS criteria are no longer part of the definition. The task force cited their inadequate sensitivity and specificity [1].

SOFA: the reference for organ dysfunction

The Sequential Organ Failure Assessment score was introduced in 1996 by a European Society of Intensive Care Medicine working group [2]. It scores six organ systems from 0 to 4:

The total runs from 0 to 24. Because it needs lab results and a blood gas, SOFA fits the ICU and the definition better than a quick bedside check.

SOFA-2 (2025)

In October 2025, SOFA-2 was published as the first major revision in 30 years [3]. It keeps the six organ systems but updates variables and thresholds to reflect modern organ support. It was developed and validated on more than 3.3 million ICU patients from 1,319 units in nine countries. Discrimination for ICU mortality was AUROC 0.79, compared with 0.77 for the original SOFA [3].

Whether and when SOFA-2 replaces SOFA in the sepsis definition is still open at the time of writing. For exams, the original SOFA remains the reference.

qSOFA: quick, but not a screening test

Quick SOFA was designed for patients outside the ICU [1, 4]. One point each for:

• respiratory rate ≥22/min
• altered mentation
• systolic blood pressure ≤100 mmHg

A score of 2 or more marks a substantially higher risk. In the validation study, qSOFA ≥2 was associated with a 3- to 14-fold increase in hospital mortality across baseline risk deciles [4].

How good is it? Outside the ICU, in patients with suspected infection, qSOFA predicted in-hospital mortality slightly better than SOFA or SIRS (AUROC 0.81 vs 0.79 vs 0.76). Inside the ICU, SOFA was clearly better (0.74 vs 0.66 for qSOFA) [4]. The authors framed qSOFA as a prompt to consider sepsis.

The catch: qSOFA often turns positive late. The SSC 2021 recommends against using qSOFA, compared with SIRS, NEWS or MEWS, as a single screening tool for sepsis or septic shock [5]. A positive qSOFA should make you think of sepsis; a negative one does not exclude it.

Calculator: qSOFA.

NEWS2: an early warning score for everyone

The Royal College of Physicians' National Early Warning Score 2 (2017) is a general deterioration score rather than a sepsis-specific one [6]. It uses six parameters (respiratory rate, SpO₂, systolic blood pressure, pulse, consciousness or new confusion, temperature) and adds 2 points for supplemental oxygen.

Thresholds [7]:

• ≥5: urgent clinical review. In anyone with suspected infection, think sepsis.
• ≥7: emergency response from a team with critical care skills.
• 3 in a single parameter: clinician review.

Because NEWS2 is calculated from routine observations and repeated at every set, the trend is what makes it useful for screening on wards and in the emergency department.

SIRS: historically important, still useful as a screen

The SIRS criteria come from the 1991 consensus conference [8]: temperature >38 °C or <36 °C, heart rate >90/min, respiratory rate >20/min or PaCO₂ <32 mmHg, white cell count >12,000/µL or <4,000/µL or >10% immature forms. Two or more criteria defined SIRS.

SIRS is sensitive but non-specific: many patients with uncomplicated infection, or after surgery, meet it [1]. It no longer defines sepsis, but it remains in use as a screening element, and the SSC names it explicitly as an alternative to qSOFA [5].

Side-by-side comparison

What the guidelines say

Surviving Sepsis Campaign 2021

The SSC 2021 [5]:

• recommends screening programmes for sepsis in acutely ill, high-risk patients, but against qSOFA as a single screening tool;
• recommends immediate antimicrobials, ideally within one hour, for possible septic shock or a high likelihood of sepsis;
• for possible sepsis without shock, suggests a time-limited rapid assessment and, if concern persists, antimicrobials within three hours.

German S3 guideline, 2025 update

For readers in Germany, Austria and Switzerland, the 2025 German S3 sepsis guideline (version 4.0) adapts the SSC 2021 to the local setting [9]. Its key points:

• Hospitals should run a sepsis quality programme with screening of high-risk patients and standard operating procedures. Outside the ICU, patients with suspected infection should be screened regularly with a suitable tool. The guideline lists qSOFA, SIRS, MEWS and NEWS/NEWS2 side by side without mandating one.
• Measure lactate in suspected sepsis.
• Take at least two sets of blood cultures before antibiotics, without materially delaying treatment.
• Give antimicrobials as early as possible, ideally within one hour in septic shock; in suspected sepsis without shock, investigate promptly and give antimicrobials within three hours if infection is still suspected.
• In sepsis-induced hypoperfusion or septic shock, give 30 mL/kg crystalloid within the first three hours as a guide, then further fluid only while hypoperfusion persists.
• Target an initial MAP of 65 mmHg in patients on vasopressors.

A practical approach

1. Think sepsis in every infection, especially in older, immunosuppressed and post-operative patients.
2. Screen with a sensitive tool, such as NEWS2, and repeat observations.
3. Treat qSOFA ≥2 as a red flag for immediate senior review. A score below 2 is not reassurance.
4. Look for organ dysfunction objectively: lactate, blood gas, creatinine, bilirubin, platelets, i.e. the components of SOFA.
5. Do not delay time-critical steps: blood cultures, antimicrobials, source identification and control.

This is a learning framework, not a protocol for an individual patient. Follow the guideline and your local pathway.

Bottom line

No single score catches every case of sepsis. SOFA defines it, qSOFA warns of a poor course, and early warning scores like NEWS2 do the screening. Repeated observations, a low threshold for suspicion and fast action once suspicion is confirmed matter more than any single number.

To look up details from the SSC or the German S3 guideline, Medelix answers with citations you can check in the original. Related tools: qSOFA, Glasgow Coma Scale, and more scores in 10 emergency department scores.

Sources

1. Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801–810. doi:10.1001/jama.2016.0287 · PMC4968574
2. Vincent JL, Moreno R, Takala J, et al. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. Intensive Care Med. 1996;22(7):707–710. doi:10.1007/BF01709751
3. Ranzani OT, Singer M, Salluh JIF, et al. Development and Validation of the Sequential Organ Failure Assessment (SOFA)-2 Score. JAMA. 2025;334(23). doi:10.1001/jama.2025.20516 · PMC12573119
4. 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):762–774. doi:10.1001/jama.2016.0288 · PMC5433435
5. Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock 2021. Crit Care Med. 2021;49(11):e1063–e1143. doi:10.1097/CCM.0000000000005337 · SCCM overview
6. Royal College of Physicians. National Early Warning Score (NEWS) 2. rcp.ac.uk
7. NHS Greater Glasgow and Clyde. NEWS2 Guideline (based on RCP 2017). 2020. PDF
8. Bone RC, Balk RA, Cerra FB, et al. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM Consensus Conference Committee. Chest. 1992;101(6):1644–1655. doi:10.1378/chest.101.6.1644
9. Deutsche Sepsis-Gesellschaft (lead). S3-Leitlinie Sepsis – Prävention, Diagnose, Therapie und Nachsorge, Update 2025, short version 4.0 [German S3 guideline]. AWMF register no. 079-001. PDF, AWMF register