SIRS, SOFA, qSOFA, and MEWS — The Alphabet Soup

5/15/18 8:00 AM

Sepsis plagues many patients and hospitals, and can be difficult to diagnose as many of its symptoms are often mistaken for other conditions such as simple infections. Furthermore, sepsis is hard to define (see JAMA for latest consensus around defining sepsis) and there is no consistent use of sepsis-related terminology, making sepsis cases all the more difficult to treat and diagnose. Sepsis also has varying presentations and diagnosis is usually based on evaluation of symptoms, patient history, and laboratory tests; there is no standard for diagnosing and treating sepsis. Due to these problems, patients often suffer long periods of time before being diagnosed and only receive treatment well after the onset of major symptoms.

Diagnosis of sepsis typically doesn’t take place until the onset of severe symptoms, as the most common scoring systems to diagnose sepsis — SIRS, SOFA, qSOFA, and MEWS (Modified Early Warning System) — are not predictive and suspicion of sepsis must already exist. Let’s dive deeper into these severity scoring systems.

SIRS, Systemic Inflammatory Response Syndrome, was coined in a 1991 consensus conference and is one of the earliest definitions for sepsis. SIRS is comprised of four criteria (learn more about SIRS):

  • Temperature less than 96.80° F OR greater than 101.40° F
  • Heart rate greater than 90 beats per minute
  • Tachypnea greater than 20 breaths per minute OR partial pressure of CO2 less than 32 mmHg
  • White blood count less than 4,000 per microliter OR greater than 12,000 per microliter OR greater than 10% immature forms

According to this definition, if patients exhibit two or more of these criteria, they have sepsis. These criteria do help physicians take action, but they lack specificity as they may suggest the presence of other indications such as trauma, burns, and ischemia. SIRS is considered by many to be limited in its approach to sepsis as it places too much emphasis on inflammation.

Another method of diagnosis is the SOFA, Sequential (Sepsis-Related) Organ-Failure Assessment, score system. A score of two or more (see chart below) and a suspicion of infection is indicative of sepsis.

Source — The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3)

SOFA is preferred over SIRS since it allows clinicians to identify organ dysfunction and can also account for clinical intervention. Drawbacks to this method include the need for laboratory variables such as creatine and bilirubin levels, and the need for a clinician to suspect sepsis beforehand.

qSOFA or Quick SOFA, is a shortened version of SOFA and intended for non-ICU patients. Under this scoring system a clinician must already suspect sepsis and the following criteria must be met:

  • Respiratory rate greater than or equal to 22 breaths per min
  • Altered mental status
  • Systolic blood pressure less than or equal to 100 mmHg

Source: National Heart, Lung, and Blood Institute

Lastly, MEWS or Modified Early Warning System, is a sepsis scoring system that is commonly used in the United Kingdom. This scoring system comprises six vital signs — respiratory rate, heart rate, systolic blood pressure, consciousness level, temperature, and hourly urine output — that are used to identify patients that are at a high risk of developing sepsis.

Source — rn.com

When a MEWS score is calculated, each vital sign is assigned a value between zero and three, based on the table above. Then, those values are then summed together to generate a MEWS score. A score greater than or equal to four is often used to call the Rapid Response Team to the bedside. Drawbacks to MEWS include a lack of specificity and sensitivity for sepsis recognition.

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