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New Definition and Guidelines for Sepsis

Dr Russell Allan Consultant in Acute Medicine and Intensive Care Medicine

Sepsis is defined as organ dysfunction due to dysregulated host response to infection. Since 2001 it had been diagnosed using the presence of Systemic Inflammatory Response Syndrome (SIRS) + suspected bacteraemia. These diagnostic criteria have however been criticised as they lack specificity (i.e. a bad cold could give rise to SIRS which reflects a host’s normal response, rather than ‘dysregulated response’ to infection). In contrast to this mild viral infection, the term sepsis conjures up the impression of a severe and life-threatening illness. As such, new diagnostic criteria were proposed based on easily obtainable data points which are associated with the individual dying or requiring ICU. This is known as the sepsis 3.0 classification:

Suspected infection and a change in SOFA score of >/= 2

Sepsis 3.0 is most useful to allow consistent coding thereby making comparisons between hospitals more accurate. In clinical practice the calculation of Sequential Organ Failure Assessment (SOFA) score in everyone at risk of sepsis can be time consuming. Therefore, a quick screening score was introduced known as qSOFA. qSOFA is a score from 0-3 based on how many of the following are present:

  • Hypotension (SBP<100 mmHg)
  • Altered conscious level
  • Tachypneoa (RR> 22 breaths / min)

The suggestion is that when 2 or more of these are present the full SOFA score should be calculated to identify sepsis. Furthermore, the presence or absence of these can be used as mortality predictors (see table 1).

Table 1 – Correlation between qSOFA and predicted mortality (1)

No. of qSOFA elements present in patient with infection Predicted mortality
0 <1%
1 2-3%
2 8%
3 20%
Sepsis shock present (see below) 40%

Note however how this table compares to table 2:

Table 2 – Sensitivity and specificity of severity scoring systems predicting requirement for critical care/death in patients with infection (1)

Scoring system Sensitivity for death or requiring Critical Care Specificity for death or requiring Critical Care
qSOFA >/=2 54% 67%
SIRS 91% 13%
NEWs >7 77% 57%
NEWs >8 67% 66%
NEWs >9 54% 78%

NEWs = National Early warning score

It must be remembered that using SIRS, SOFA or qSOFA scores do not aid the identification of infection but if infection is the cause of the deranged physiology then they define sepsis. As such, when used alone (without the assessment of ‘is infection present’) they have various sensitivities and specificities for infection depending on the population studied.

Septic shock

Another marker of severity is the presence of septic shock. This is now defined by sepsis 3.0 as sepsis with circulatory and cellular/metabolic abnormalities and diagnosed by persistent hypotension and a lactate level which is still > 2 after adequate fluid resuscitation. This is slightly different than the previous definition where persistent lactate elevation was not necessary. The presence of this new septic shock definition predicts mortality at 40%. The term severe sepsis no longer exists in the sepsis 3.0 definition (all sepsis is severe).

Now that you’ve had a brief introduction to the new definitions of Sepsis, what do you think the pros and cons of these are? Discuss your thoughts with your peers in the comments section below.


  1. Churpek, M.M, Snyder A, Ha, X, Sokol S, Pettit N, Howel M.D, Edelson D.P. Quick Sepsis-related Organ Failure Assessment, Systemic Inflammatory Response Syndrome, and Early Warning Scores for Detecting Clinical Deterioration in Infected Patients outside the Intensive Care Unit. American Journal of Respiratory and Critical Care Medicine.2017;195(7): 906-911.

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This article is from the free online course:

Introduction to Critical Care Medicine

The University of Glasgow