SIRS is the body's systemic inflammatory response to a variety of insults including infection, trauma, burns, pancreatitis, and surgery. It is defined by meeting 2 or more of 4 criteria: abnormal temperature, tachycardia, tachypnea or low PaCO₂, and abnormal WBC count. SIRS with a suspected source of infection was historically called sepsis.

Is SIRS still used in sepsis diagnosis?

The Sepsis-3 definition (2016) replaced SIRS-based sepsis criteria with the SOFA score approach. However, SIRS criteria remain clinically valuable for early detection of inflammatory states and are still used in many hospitals as screening tools. Many studies continue to reference SIRS criteria.

What are the limitations of SIRS?

SIRS criteria are highly sensitive but not specific — many non-infectious conditions trigger SIRS (post-surgical, trauma, pancreatitis). Up to 50% of hospitalized patients may meet SIRS criteria without infection. The high false-positive rate led to the development of qSOFA and SOFA-based definitions for sepsis.

Online Medical Tools — SIRS Criteria

Printed on 2/13/2026

For informational purposes only. This is not medical advice.

Emergency

SIRS Criteria

The Systemic Inflammatory Response Syndrome (SIRS) criteria were defined in 1992 as a set of four clinical findings that indicate a generalized inflammatory process. SIRS is present when two or more criteria are met: temperature >38°C or <36°C, heart rate >90 bpm, respiratory rate >20 or PaCO₂ <32 mmHg, and WBC >12,000 or <4,000 or >10% bands. While Sepsis-3 (2016) moved to SOFA-based definitions, SIRS criteria remain widely referenced and used in many clinical settings for early identification of inflammatory states.

Compare with qSOFA Score

Formula: SIRS = sum of 4 criteria (each 0 or 1). SIRS positive ≥ 2.

How to Interpret Your Result

Your result indicates whether the Systemic Inflammatory Response Syndrome (SIRS) criteria are met. Meeting two or more of the four criteria (abnormal temperature, tachycardia, tachypnea or low PaCO2, abnormal WBC) defines SIRS-positive status. A SIRS-positive result indicates that the body is mounting a systemic inflammatory response, which may be due to infection (sepsis), trauma, burns, pancreatitis, surgery, or other inflammatory conditions.

A SIRS-negative result (0–1 criteria met) suggests the patient does not currently display a generalized inflammatory response, though this does not rule out localized infection or early systemic disease. Serial reassessment is important because SIRS status can change rapidly as the clinical picture evolves.

When to Use This Tool

Use the SIRS criteria as a bedside screening tool for early identification of systemic inflammation in acutely ill patients. It is most commonly applied in the emergency department, surgical settings, and inpatient wards when evaluating patients with suspected infection, post-operative fever, trauma, or other conditions that may trigger a systemic inflammatory response.

Although the Sepsis-3 definition (2016) moved toward SOFA-based criteria for defining sepsis, SIRS criteria remain valuable for initial screening, particularly in settings where laboratory values for SOFA are not immediately available. Many hospitals still use SIRS-based screening protocols as part of sepsis alert systems. The criteria are also widely used in clinical research and as inclusion criteria for clinical trials.

Limitations

SIRS criteria are highly sensitive but poorly specific for infection. Up to 50% of hospitalized patients — particularly post-surgical patients, trauma patients, and those in the ICU — may meet SIRS criteria without having an infection. This high false-positive rate was a major reason the Sepsis-3 task force moved to SOFA-based definitions for sepsis.

Conversely, some patients with serious infections (particularly elderly or immunocompromised patients) may not mount a SIRS response, leading to false negatives. The criteria also do not differentiate between infectious and non-infectious causes of inflammation. For sepsis-specific screening, qSOFA or the full SOFA score may provide better specificity. SIRS criteria should always be interpreted alongside clinical context, not used as a standalone diagnostic tool.

Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.