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In 2016, the Third International Consensus Definitions for Sepsis and Septic Shock, known as Sepsis-3, redefined sepsis as life-threatening organ dysfunction caused by infection, whether confirmed or suspected. This replaced the earlier Sepsis-2 (2001) definition, which described sepsis as a systemic inflammatory response syndrome (SIRS) due to infection.
Since the Sepsis-3 guidelines were introduced, there has been ongoing debate among healthcare providers in the United States about whether to adopt them, due to several factors:
The following explains why the Sepsis-2/SIRS criteria are no longer considered the standard for identifying sepsis.
Dr. Marvyn Singer, the lead author of the Sepsis-3 definition, was the guest speaker at our special session on November 6, 2025, titled “Sepsis-3: Insights from the Lead Author.” Dr. Singer discussed the rationale behind removing SIRS from the diagnostic criteria and clarified that the SOFA score for identifying acute organ dysfunction is applicable to all patients presenting with infection.
Dr. Singer cited the Sepsis-3 guidelines: “The current use of 2 or more SIRS criteria to identify sepsis was unanimously considered by the task force to be unhelpful. Changes in white blood cell count, temperature, and heart rate reflect inflammation, the host response to “danger” in the form of infection or other insults. The SIRS criteria do not necessarily indicate a dysregulated, life-threatening response. SIRS criteria are present in many hospitalized patients, including those who never develop infection and never incur adverse outcomes (poor discriminant validity).”
Specifically, SIRS criteria are non-specific and may be present with any form of illness. Changes in WBC, temperature and heart rate are normal inflammatory responses. SIRS definitions are inconsistent with the current understanding of sepsis pathophysiology. Research showed that one in eight patients admitted to CCUs with infection and acute organ failure did not have the requisite 2 SIRS criteria. Notably, a 2017 study of U.S. claims data from 2009-2014 found a 50% increase in sepsis coding using SIRS, without change in clinical outcomes, suggesting overrepresentation of clinical sepsis using SIRS.
Sepsis-3 criteria more accurately identify infected patients likely to have bad outcomes. Sepsis-3 is based on analysis of a large patient database, whereas the SIRS criteria were elaborated empirically. Sepsis-3 is widely accepted in the scientific community and cited in almost 19,000 studies. Sepsis-3 serves as a “steppingstone” to support research for eventually defining a more precise definition for a potential Sepsis-4 definition.
To further demonstrate that SIRS criteria are no longer considered the standard for sepsis identification, the 2024 pediatric sepsis update, International Consensus Criteria for Pediatric Sepsis and Septic Shock, also eliminated SIRS as a diagnostic criterion. The revised pediatric sepsis definition aligns with Sepsis-3, defining sepsis as life-threatening organ dysfunction resulting from infection, and explicitly states that "the former criteria based on systemic inflammatory response syndrome should not be used to diagnose sepsis in children" and "the former term 'severe sepsis' should no longer be used." Whereas Sepsis-3 utilizes the SOFA score to assess organ dysfunction, the newly established Phoenix score has been adopted for identifying organ dysfunction in pediatric patients.
In 2015, the CMS introduced the Severe Sepsis and Septic Shock: Early Management Bundle (SEP-1) as a hospital-based sepsis quality measure. The SEP-1 measure includes SIRS criteria, as well as acute organ dysfunction, as the clinical criteria to identify potential severe sepsis. Of note, these diagnostic screening criteria were implemented before the release of the Sepsis-3 guidelines and have not changed since 2015. Because SEP-1 incorporates SIRS criteria, many hospitals still regard the Sepsis-2 SIRS criteria as the official CMS standard for identifying sepsis.
The CMS SEP-1 measure serves as a screening tool to facilitate early intervention for the prevention of severe sepsis and is not intended to function as diagnostic criteria. SEP-1 criteria that activate the treatment bundle—comprising specific interventions required within a strict timeframe—include documentation of a suspected infection in addition to at least two SIRS criteria and at least one new organ dysfunction, all documented within a six-hour window. The purpose of this treatment protocol is to decrease mortality by ensuring that patients exhibiting these clinical indicators receive prompt administration of IV antibiotics, blood culture collection, lactate measurement, and IV fluids if septic shock is suspected. Should a patient be admitted with these criteria and the hospital files a claim with a sepsis ICD-10 code, these interventions are expected to have been performed. If subsequently it is determined that the patient does not have severe sepsis and sepsis is not included as a diagnosis code on the claim, these cases are excluded from the quality measure. Consequently, meeting these SEP-1 clinical criteria alone does not confirm a diagnosis of sepsis or severe sepsis.
Medicare coverage determinations, including Local Coverage Determinations (LCDs) and National Coverage Determinations (NCDs), outline the conditions under which items or services are considered medically necessary and appropriate. These determinations refrain from dictating the diagnostic criteria or treatment guidelines that clinicians must follow when diagnosing patients with covered conditions. Generally, Medicare coverage policies identify eligible diagnoses using ICD-10-CM codes for particular services; nevertheless, CMS does not mandate the diagnostic criteria clinicians should apply for patient diagnosis.
In the 2024 Final Rule, CMS addressed Medicare Advantage (MA) organizations and coverage criteria, stating: “When Medicare coverage criteria are not fully established, MA organizations may create publicly accessible internal coverage criteria that are based on current evidence from widely used treatment guidelines or clinical literature.”
The Office of the Inspector General (OIG), which oversees waste, fraud, and abuse in Health and Human Services (HHS) programs—including CMS and Medicare—has announced plans to review “Medicare Inpatient Hospital Billing for Sepsis” in its latest work plan. This initiative states that: “The definition of and guidance for sepsis have changed over the years in attempts to identify it more accurately. The definition of sepsis was updated in 2016 by an international task force to better differentiate sepsis from a general infection. This narrower definition is widely recognized by groups such as the World Health Organization. However, CMS and CDC currently recognize an older, broader definition. Sepsis is a frequently billed diagnosis in Medicare. There are concerns that hospitals may be taking advantage of this broader definition, as they have a financial incentive to do so.”
The diagnostic criteria utilized by auditors selected by the OIG for reviewing hospital billing related to sepsis will be of particular interest. The findings from this review are anticipated to be published in 2026.
In the meantime, sepsis remains one of the most frequently denied diagnoses by payers in the United States. Most of these denials are based on the continued use of Sepsis-2 SIRS criteria by hospitals despite the adoption of the Sepsis-3/SOFA criteria in 2017.
Hospitals and providers are encouraged to adopt both the Sepsis-3 and updated pediatric sepsis definitions to properly identify and classify patients for research and payment purposes. The Sepsis-3 guidelines can be used at the same time as the CMS SEP-1 Severe Sepsis treatment bundle, which allows organizations to meet both the SEP-1 core measure and the Sepsis-3 diagnostic standards.
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