Systemic Inflammatory Response Syndrome (SIRS)
Helps diagnose SIRS based on clinical data about immune response.
In the text below the calculator there is more information about the diagnosis criteria and how it should be interpreted.
The SIRS criteria diagnoses systemic inflammatory response based on clinical parameters such as temperature, heart rate, white blood cell count or hyperglycemia.
The criteria can be used in adult patients that are suspected of infection. It was used between 1992 and 2016, for early detection of sepsis (now is replaced by qSOFA score for sepsis diagnosis).
SIRS causes are classified as infectious and non-infectious. Most common non-infectious causes leading to SIRS include: trauma, pancreatitis, haemorrhage, ischemia or burns.
Infectious causes are defined as bacteremia in the bloodstream. Severe sepsis is accompanied by organ dysfunction, hypotension and hypoperfusion.
Left untreated, it can lead to acute lung or kidney injury, acute respiratory distress syndrome (ARDS) or multiple organ dysfunction syndrome.
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SIRS criteria explained
This clinical tool consists of the diagnosis criteria for systemic inflammatory response syndrome.
An American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference held in Northbrook in 1991 created consensus on a set of definitions that could be applied to patients with sepsis and its sequelae.
Broad definitions of sepsis and the systemic inflammatory response syndrome were proposed and associated with clinical parameters to be monitored in patients.
The response of the immune system to infection or other illness is reflected through the following:
| SIRS parameter | Description |
| Body temperature | Temperature less than 36°C (96.8°F) or greater than 38°C (100.4°F) are considered risk factors. Fever is characteristic to the acute phase reaction. |
| Heart rate | Increased heart rate (greater than 90 bpm) is suggestive of hemodynamic compromise. |
| Tachypnea | Is defined as high respiratory rate with more than 20 breaths per minute either due to increased metabolic stress or inadequate perfusion. |
| White blood cell count | WBC less than 4,000 cells/mm³ (4 x 109 cells/L) or greater than 12,000 cells/mm³ (12 x 109 cells/L) as sign of inflammation. |
| Immature neutrophils | Presence of greater than 10% immature neutrophils (band forms). |
| Hyperglycemia | Blood glucose greater than 120 mg/dL or 6.66 mmol/L in absence of diabetes mellitus diagnosis. |
| Acutely altered mental state | As evidenced during clinical examination. |
The patient is considered positive for SIRS if a minimum of two of the above criteria are met.
The main criticism of the model refers to the fact that is mainly unspecific, cannot offer full diagnosis or any treatment recommendations.
Between 1992 and 2016, these criteria were also used for the early detection of sepsis when a minimum of 2 criteria are present along with a suspected source of infection.
The severe sepsis criteria was deemed positive when 2 SIRS plus lactic acidosis plus increased blood pressure are present.
Multiple organ dysfunction syndrome was deemed positive when there are at least 2 SIRS criteria and evidence of two or more organs failing.
Guideline updates
In February 2016, these criteria have ceased being recommended for diagnosis of sepsis, because of a lack of sensitivity and specificity. These have been replaced by qSOFA, a simpler scoring system with three criteria:
■ Altered Mental Status (GCS <15) – assessed through bedside Glasgow coma scale with the 15 points cut off value between abnormal and normal.
■ Respiratory Rate ≥22 breaths per minute – increased respiratory rate.
■ Systolic Blood Pressure ≤100 mmHg – lowered SBP.
This is a shorter version of the Sequential [Sepsis-related] Organ Failure Assessment (SOFA) score applicable in intensive care units.
Sepsis is now defined as a "life-threatening organ dysfunction due to a dysregulated host response to infection" by the Third International Sepsis Consensus Definitions Task Force.
SIRS causes and complications
The main classification of SIRS causes is made between infectious and non-infectious. Infectious causes lead to a systemic inflammatory response syndrome and this is often reunited under the term sepsis (bacteremia within the bloodstream). Patients with severe sepsis suffer from organ dysfunction, hypotension and hypoperfusion.
Most common non-infectious causes include trauma, pancreatitis, ischemia, burns and hemorrhage.
Left untreated SIRS leads to acute lung or kidney injury, acute respiratory distress syndrome (ARDS), shock and multiple organ dysfunction syndrome.
There are several complications associated with SIRS: adrenal insufficiency, cardiac tamponade, pulmonary embolism or anaphylaxis.
Complications usually vary depending on the underlying etiology. Clinical prophylaxis is usually put in place for in-hospital patients, against DVT, stress ulcer and to lower risk of super infections.
Original sources
1. Bone RC, Balk RA, Cerra FB, Dellinger RP, Fein AM, Knaus WA, Schein RM, Sibbald WJ. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM Consensus Conference Committee. American College of Chest Physicians/Society of Critical Care Medicine. Chest. 1992; 101(6):1644-55.
2. International Guidelines for Management of Severe Sepsis and Septic Shock: 2012.
Other references
1. Levy MM, Fink MP, Marshall JC, Abraham E, Angus D, Cook D, Cohen J, Opal SM, Vincent JL, Ramsay G. 2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference. Crit Care Med. 2003; 31(4):1250-6.
2. Balk RA. Systemic inflammatory response syndrome (SIRS). Where did it come from and is it still relevant today? Virulence. 2014; 5(1): 20–26.
3. Kaukonen KM, Bailey M, Pilcher D, Cooper DJ, Bellomo R. Systemic inflammatory response syndrome criteria in defining severe sepsis. N Engl J Med. 2015; 372(17):1629-38.
Specialty: Emergency
Objective: Diagnosis
Type: Criteria
No. Of Criteria: 10
Year Of Study: 1992
Abbreviation: SIRS
Article By: Denise Nedea
Published On: June 18, 2017 · 02:30 PM
Last Checked: June 18, 2017
Next Review: June 18, 2023