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Patient-level reclassification and discordance between SOFA and SOFA-2: a multicenter ICU study
Shohei Ono1,2, Shigehiko Uchino3, Yutaka Kumaido3,4
1Department of Anesthesiology and Critical Care Medicine, Jichi Medical University Saitama Medical Center, Saitama, Japan. airness.of.mj@gmail.com.
Background:
The Sequential Organ Failure Assessment (SOFA) score is widely used to quantify organ dysfunction in critically ill patients. A revised version, SOFA-2, was proposed to better reflect contemporary intensive care practice, but patient-level reclassification and the implications of differences between SOFA and SOFA-2 remain unclear.
Methods:
We conducted a retrospective multicenter cohort study using the OneICU database, a Japanese ICU registry including 15 hospitals. Adult ICU admissions between April 2012 and December 2025 were analyzed. Day-1 SOFA and SOFA-2 scores were calculated. Reclassification patterns were visualized using Sankey diagrams, and mortality patterns were assessed using heat maps. Score discordance was defined as SOFA deviation (dSOFA = SOFA-2 - SOFA) and categorized as Negative ( ≤ - 2), Minimal ( > - 2 and < 2), or Positive (≥ 2). Two primary exact-matching analyses were performed across dSOFA categories, separately matching patients on Day-1 SOFA-2 and conventional SOFA total scores.
Results:
Among 134,528 ICU admissions, SOFA-2 resulted in systematic patient-level reclassification. Upward shifts were most frequent in the brain, cardiovascular, and respiratory subscores, whereas the kidney subscore showed bidirectional changes. Mortality increased with higher SOFA-2 subscores at fixed SOFA and with higher SOFA subscores at fixed SOFA-2. After exact matching on SOFA-2, mortality was highest in the Negative dSOFA group, in which SOFA was higher than SOFA-2. Conversely, after exact matching on conventional SOFA, mortality was highest in the Positive dSOFA group, in which SOFA-2 was higher than SOFA.
Conclusions:
SOFA-2 introduces systematic reclassification at the patient level. Reciprocal exact-matching analyses demonstrated that patients assigned the same severity by one scoring system remained heterogeneous in mortality according to the other scoring system. SOFA and SOFA-2 may therefore provide overlapping but complementary information for assessing organ dysfunction severity.
Insights
The revised Sequential Organ Failure Assessment (SOFA-2) score systematically reclassifies patients, showing that SOFA and SOFA-2 offer complementary insights into organ dysfunction severity in critical care.
Area of Science:
- Intensive care medicine
- Clinical epidemiology
- Health informatics
Background:
- The Sequential Organ Failure Assessment (SOFA) score is a standard tool for assessing organ dysfunction in critically ill patients.
- A revised SOFA-2 score was developed to align with current intensive care practices.
- The impact of SOFA-2 on patient classification and its relationship with mortality compared to the original SOFA score require clarification.
Purpose of the Study:
- To evaluate patient-level reclassification by SOFA-2 compared to the conventional SOFA score.
- To investigate the association between score discordance (dSOFA) and mortality.
- To determine if SOFA and SOFA-2 provide overlapping or complementary prognostic information.
Main Methods:
- Retrospective analysis of 134,528 adult ICU admissions from a Japanese multicenter registry (OneICU database).
- Calculation of Day-1 SOFA and SOFA-2 scores, with visualization of reclassification patterns using Sankey diagrams and mortality using heat maps.
- Exact-matching analyses were performed across SOFA deviation (dSOFA) categories, matching on both SOFA-2 and SOFA scores to compare mortality.
Main Results:
- SOFA-2 led to systematic patient reclassification, with notable upward shifts in brain, cardiovascular, and respiratory subscores, and bidirectional changes in the kidney subscore.
- Mortality patterns differed significantly based on the scoring system used for matching: highest mortality in the Negative dSOFA group (SOFA > SOFA-2) when matched on SOFA-2, and in the Positive dSOFA group (SOFA-2 > SOFA) when matched on SOFA.
- Patients with identical scores under one system exhibited heterogeneous mortality outcomes when assessed by the other system.
Conclusions:
- SOFA-2 introduces significant patient-level reclassification compared to the conventional SOFA score.
- Reciprocal matching analyses reveal that SOFA and SOFA-2 capture distinct aspects of organ dysfunction severity, leading to different mortality associations.
- The findings suggest that SOFA and SOFA-2 provide complementary, rather than interchangeable, information for prognostication in critically ill patients.