SOFA Score (Sequential Organ Failure Assessment)

Overview

The SOFA score (Sequential Organ Failure Assessment), originally called the Sepsis-related Organ Failure Assessment, was developed by Vincent et al. in 1996 to describe and quantify the degree of organ dysfunction in critically ill patients ^[1]. It evaluates six organ systems — respiratory, coagulation, hepatic, cardiovascular, central nervous system, and renal — each scored 0 (normal) to 4 (severe dysfunction), yielding a total of 0–24 points. A multicenter validation across 40 ICUs in 16 countries (n = 1,449) confirmed the score's ability to track organ dysfunction over time ^[2].

SOFA gained renewed prominence with the Sepsis-3 consensus in 2016, which defined sepsis as a life-threatening organ dysfunction caused by a dysregulated host response to infection ^[4]. Sepsis is now operationally identified by an acute increase in SOFA score of ≥ 2 points, corresponding to an estimated hospital mortality of over 10% — a figure derived from a large retrospective cohort analysis conducted specifically to validate the clinical criteria ^[5]. This replaced the former SIRS-based definition.

SOFA can be used as both a static snapshot (absolute score) and a dynamic measure (change over time). Rising SOFA scores during ICU admission are strongly associated with worsening prognosis, while falling scores may reflect treatment response ^[3].

Scoring Table

System / Parameter	0	1	2	3	4
Respiration PaO₂/FiO₂ (mmHg)	≥ 400	< 400	< 300	< 200 + resp. support	< 100 + resp. support
Coagulation Platelets (×10³/µL)	≥ 150	< 150	< 100	< 50	< 20
Liver Bilirubin (mg/dL)	< 1.2	1.2 – 1.9	2.0 – 5.9	6.0 – 11.9	≥ 12.0
Cardiovascular MAP / vasopressors	MAP ≥ 70	MAP < 70	Dopa ≤ 5 or Dobu any	Dopa > 5–15 or Epi/Norepi ≤ 0.1	Dopa > 15 or Epi/Norepi > 0.1
CNS Glasgow Coma Scale	15	13 – 14	10 – 12	6 – 9	< 6
Renal Creatinine (mg/dL)	< 1.2	1.2 – 1.9	2.0 – 3.4	3.5 – 4.9	≥ 5.0
Renal Urine output (mL/day)	≥ 500	—	—	< 500	< 200

Vasopressor doses in µg/kg/min. For the renal system, the worse of creatinine and urine output scores is used. Respiratory scores 3 and 4 require confirmed respiratory support (mechanical ventilation or CPAP) — without it, the respiratory sub-score is capped at 2 regardless of the PaO₂/FiO₂ ratio.

Interpretation

Total SOFA	Estimated Hospital Mortality
0 – 6	< 10 %
7 – 9	~15 – 20 %
10 – 12	~40 – 50 %
13 – 14	~50 – 60 %
≥ 15	> 80 %

This table is a commonly used composite summary (matching how it is presented by other clinical calculator references) rather than a single table reproduced verbatim from one paper — the original multicenter validation and the serial-evaluation follow-up report related but not identically-binned figures ^[2]^[3], and very high scores (SOFA > 15) have also been reported at closer to 90% mortality in some analyses of the original cohort. Treat these percentages as an approximate, population-level guide, not a precise per-patient prediction (see Scientific Validity & Limitations below).

Sepsis-3 criterion: An acute increase in SOFA score of ≥ 2 points from baseline in a patient with suspected infection identifies organ dysfunction and meets the definition of sepsis, with an expected mortality exceeding 10 % ^[4]^[5]. The qSOFA score (≥ 2 of: RR ≥ 22, altered mentation, SBP ≤ 100) can be used outside the ICU to prompt further evaluation.

Scientific Validity & Limitations

SOFA's cardiovascular component still reflects 1996-era vasopressor practice, scored primarily around dopamine dosing. Contemporary Surviving Sepsis Campaign guidance favors norepinephrine as first-line, and a 2022 Korean Shock Society study derived and validated a "modified cardiovascular SOFA" using norepinephrine-equivalent dosing across all vasopressors, arguing the classic dopamine-centric table under-represents cardiovascular dysfunction in units that rarely use dopamine ^[7]. Scores2Go implements the classic 1996 table, which remains the version used by MDCalc and referenced in current sepsis guidelines, but this is a recognized limitation worth being aware of.

A 2008 systematic review of SOFA-based mortality-prediction models found substantial heterogeneity in how studies convert SOFA into a mortality estimate, and limited external validation of any single conversion across independent cohorts ^[6] — consistent with why the interpretation table above should be read as an approximate guide rather than a precisely validated probability. More broadly, ICU severity scores including SOFA are designed and validated for population-level description and research comparison, not for prognosticating or guiding treatment in an individual patient ^[8].

Well-documented structural limitations, independent of any single validation study:

Not a treatment-limitation-adjusted score: like most organ-dysfunction scores, SOFA does not account for do-not-resuscitate status or care-limitation decisions, which independently affect observed mortality.
Dopamine-centric cardiovascular component: as above, the classic vasopressor thresholds may not map cleanly onto units where norepinephrine is used exclusively as first-line.
Requires the "worst value" convention: like other worst-value-in-24-hours scores, SOFA is sensitive to measurement frequency and to inter-observer variation in what counts as the worst value in a given window.
GCS confounded by sedation: deep sedation, common in modern ICU practice, can inflate the CNS sub-score independent of true neurologic dysfunction — MDCalc's own guidance recommends estimating the GCS a sedated patient would have off sedatives.
Static score alone is a weaker predictor than its trend: a rising SOFA score over the first 48 hours is a substantially stronger mortality signal than any single absolute value ^[3].

Literature

Vincent JL, Moreno R, Takala J, et al. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. Intensive Care Med. 1996;22(7):707–710.
Vincent JL, de Mendonça A, Cantraine F, et al. Use of the SOFA score to assess the incidence of organ dysfunction/failure in intensive care units: results of a multicenter, prospective study. Crit Care Med. 1998;26(11):1793–1800.
Ferreira FL, Bota DP, Bross A, Mélot C, Vincent JL. Serial evaluation of the SOFA score to predict outcome in critically ill patients. JAMA. 2001;286(14):1754–1758.
Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801–810.
Seymour CW, Liu VX, Iwashyna TJ, et al. Assessment of Clinical Criteria for Sepsis: For the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):762–774.
Minne L, Abu-Hanna A, de Jonge E. Evaluation of SOFA-based models for predicting mortality in the ICU: a systematic review. Crit Care. 2008;12(6):R161.
Lee HJ, Ko BS, Ryoo SM, et al.; Korean Shock Society. Modified cardiovascular SOFA score in sepsis: development and internal and external validation. BMC Med. 2022;20:263.
Vincent JL, Moreno R. Clinical review: scoring systems in the critically ill. Crit Care. 2010;14(2):207.

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