**2.2 Sequential organ failure assessment (SOFA)**

Recognizing sepsis' dependence on SIRS and its inherent limitations in characterizing end-organ damage, Sepsis-3 re-defined sepsis as a "life threatening organ dysfunction caused by a dysregulated host response to infection" and endorsed the sequential organ failure assessment (SOFA) score as a scoring system for mortality [6]. SOFA's summative score of multiple organ systems reflects PaO2/FiO2 (respiratory), platelet count (coagulation), bilirubin (liver), hypotension (cardiovascular), Glasgow coma score (GCS-neurologic), and creatinine or urine output (renal). The creators of SOFA aimed to keep it simple to allow for repeated assessments over time. The worst daily value is used to trend the risk of mortality in patients who are admitted to the intensive care unit. SOFA only uses variables that are obtained routinely and implemented a scoring system from zero to four to stratify a patient's risk rather than using binary categorization.

Key limitations to SOFA include its simplicity in characterizing only six organ systems as detailed above. It is unclear if bilirubin is the best biomarker for the hepatic system given hyperbilirubinemia takes days to manifest and is also the most frequently missing variable if the lab is not ordered [7]. GCS as a measure of neurologic function is at risk of being uninterpretable in hospitalized patients, a patient population in whom sedatives are frequently used.
