What are the diagnostic criteria for systemic inflammatory response syndrome (SIRS)?

Updated: May 07, 2018
  • Author: Lewis J Kaplan, MD, FACS, FCCM, FCCP; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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With the exception of white blood cell count abnormalities (>12,000/µL or < 4,000/µL or >10% immature [band] forms), the criteria for SIRS are based on vital signs, as follows:

  • Fever of more than 38°C (100.4°F) or less than 36°C (96.8°F)

  • Heart rate of more than 90 beats per minute

  • Respiratory rate of more than 20 breaths per minute or arterial carbon dioxide tension (PaCO2) of less than 32 mm Hg

Careful review of initial vital signs is an integral component of the diagnosis. Reassessing the vital signs periodically during the initial evaluation period is necessary, as multiple factors (eg, stress, anxiety, exertion of walking to the examination room) may lead to a false diagnosis of SIRS.

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