Measurement of sepsis in a national cohort using three different methods to define baseline organ function

Rationale: In 2017, the U.S. Centers for Disease Control and Prevention (CDC) developed a new surveillance definition of sepsis, the adult sepsis event (ASE), to better track sepsis epidemiology. The ASE requires evidence of acute organ dysfunction and defines baseline organ function pragmatically as the best in-hospital value. This approach may undercount sepsis if new organ dysfunction does not resolve by discharge. Objectives: To understand how sepsis identification and outcomes differ when using the best laboratory values during hospitalization versus methods that use historical lookbacks to define baseline organ function. Methods: We identified all patients hospitalized at 138 Veterans Affairs hospitals (2013-2018) admitted via the emergency department with two or more systemic inflammatory response criteria, were treated with antibiotics within 48 hours (i.e., had potential infection), and completed 41 days of antibiotics (i.e., had suspected infection). We considered the following three approaches to defining baseline renal, hematologic, and liver function: the best values during hospitalization (as in the Centers for Disease Control and Prevention's ASE), the best values during hospitalization plus the prior 90 days (3-mo baseline), and the best values during hospitalization plus the prior 180 days (6-mo baseline). We determined how many patients met the criteria for sepsis by each approach, and then compared characteristics and outcomes of sepsis hospitalizations between the three approaches. Results: Among 608,128 hospitalizations with potential infection, 72.1%, 68.5%, and 58.4% had creatinine, platelet, and total bilirubin measured, respectively, in the prior 3 months. A total of 86.0%, 82.6%, and 74.8%, respectively, had these labs in the prior 6 months. Using the hospital baseline, 100,568 hospitalizations met criteria for community-acquired sepsis. By contrast, 111,983 and 117,435 met criteria for sepsis using the 3- and 6-month baselines, for a relative increase of 11% and 17%, respectively. Patient characteristics were similar across the three approaches. In-hospital mortality was 7.2%, 7.0%, and 6.8% for sepsis hospitalizations identified using the hospital, 3-month baseline, and 6-month baseline. The 30-day mortality was 12.5%, 12.7%, and 12.5%, respectively. Conclusions: Among veterans hospitalized with potential infection, the majority had laboratory values in the prior 6 months. Using 3- and 6-month lookbacks to define baseline organ function resulted in an 11% and 17% relative increase, respectively, in the number of sepsis hospitalizations identified.