Screening vs Risk-Stratification Tool
SIRS and Sepsis-3
An important thing to realize about Sepsis-3 is that no Emergency Medicine physicians were a part of the assembled task force. However, ED physicians are intimately involved in the diagnosis, early management and risk-stratification of patients with presumed sepsis. The large majority of patients ultimately admitted to the ICU with sepsis or septic shock initially present to the ED, and most of these patients are identified (screened for) using the Systemic Inflammatory Response Syndrome (SIRS) criteria . “Sepsis” had therefore been defined as presence of 2 or more of the SIRS criteria, coupled with suspected infection . However, the SIRS criteria were criticized for being too non-specific, and were seen in many patients who did not have infection . Further to this, Kaukonen and colleagues  demonstrated that 1/8 of patients admitted to the ICU with severe sepsis or septic shock did not meet the SIRS criteria, and that presence of the SIRS criteria was not associated with increased mortality. Thus, both the specificity and the sensitivity of the SIRS criteria in detecting sepsis were questioned.
|SIRS Criteria > 2 or more|
Based on this, the Sepsis-3 task force chose to remove SIRS from the definition of sepsis. Instead, they chose to focus the definition on the 3 things we seem to know about sepsis with some degree of confidence: A) It starts with infection; B) It involves a complex immune-mediated host response; and C) It results in multi-system organ dysfunction. Therefore, the definition of sepsis was changed to:
At The Bedside: qSOFA
This was recognized by the Sepsis-3 task force. They used their large dataset of patients with suspected infection to retrospectively identify the major criteria, ascertainable at the bedside on initial assessment, that were most associated with death or prolonged ICU admission. This was termed the quick SOFA (qSOFA) score . The qSOFA score consists of three criteria: Hypotension (SBP ≤ 100mHg), altered mental status (GCS ≤ 13) and tachypnea (respiratory rate ≥ 22). Presence of 2 or more of these criteria was associated with significantly increased risk of death or ICU admission ≥ 72 hours.
|Image from R.E.B.E.L. EM – http://rebelem.com/sepsis-3-0/|
An important thing to realize about the qSOFA score before you apply it is that qSOFA was designed as a risk-stratification tool, NOT a screening tool. That is, it was designed to maximize specificity, not sensitivity. So the presence of 2 or more of the criteria is an ominous sign. However, absence of the qSOFA criteria should not reassure you. Since SIRS was removed from the definition by the Sepsis-3 task force, there is a temptation to use qSOFA in its place. However, SIRS is a screening tool, while qSOFA is a risk-stratification tool. They are not interchangeable . Further to that, according to the Sepsis-3 investigators, qSOFA does not replace the SOFA criteria in the diagnosis of sepsis either . Finally, it is important to know that the qSOFA score has never been prospectively applied in the ED (but stay tuned…).
The Sickest of the Sick: Septic Shock
Sepsis-3: The Take Home Messages
- We still need a screening tool to identify patients with infection. This is not addressed in Sepsis-3. While these investigators chose to remove the SIRS criteria from the definition of sepsis, it may not make sense to remove them from our ED screening (at least for now). We know that utilization of the SIRS criteria for ED screening and early initiation of treatment has been associated with improved patient outcomes .
- “Sepsis” is diagnosed by Sepsis-3 as suspected infection coupled with an acute increase in the SOFA score of 2 or more. However, the cumbersome nature of the SOFA score makes it difficult to apply in the ED.
- The qSOFA score was designed for easy application at the bedside, but it was created as a risk-stratification tool, NOT a screening tool. A qSOFA ≥ 2 should concern you, but a qSOFA < 2 should not reassure you. Do not use it as a substitute for SIRS.
- Septic Shock is now defined as initiation of vasopressors to maintain a MAP ≥ 65mmHg, coupled with a lactate > 2.0 mmol/L following “adequate fluid resuscitation”. These patients are at highest risk of death.
- Keep an eye on your initial lactate. A lactate ≥ 4.0 mmol/L has a specificity of 92% for in-hospital mortality in patients with infection .