Researchers from 28 countries have proposed updating the Sequential Organ Failure Assessment (SOFA) score to better measure organ dysfunction in critically ill patients admitted to the ICUs.

SOFA 2, the revised score, incorporates interventions that are now routinely available but did not exist when the original tool was introduced 29 years ago, including newer medications and life-support technologies.

Both scores assess hepatic, renal, cardiac, respiratory, neurologic, and blood coagulation functions. Researchers have also attempted gastrointestinal and immunologic assessments; however, they have not yielded satisfactory results.

Speaking with Medscape’s Portuguese edition, “Since 1996, ICUs and medicine have evolved a great deal,” said Otavio T. Ranzani, MD, PhD, the study’s first author. “For example, we can now replace kidney function very effectively with dialysis. When the original score was developed in 1996, dialysis was not even considered because it was not widely used at the time.”

Ranzani leads the DataHealth Lab at Institut de Recerca Sant Pau in Barcelona, Spain. He is also a researcher in the Pulmonary Division, Faculty of Medicine, Heart Institute, at Hospital das Clinicas da Faculdade de Medicina da Universidade de São Paulo in São Paulo, Brazil.

Development and Validation

The study involved 64 expert researchers in intensive care, epidemiology, and data science. The research was conducted in eight stages, beginning with a review of the original SOFA method. Divided into eight working groups and supported by systematic reviews, participants proposed updates refined through two Delphi consensus rounds, followed by application to large clinical databases. The final phase, which combined the Delphi rounds with the database analyses, was repeated until validation.

Researchers analyzed health data from more than 3.3 million patients admitted to 1319 ICUs across nine countries: Australia, Austria, Brazil, France, Italy, Japan, Nepal, New Zealand, and the US. According to the authors, the study’s strengths include its diverse working group of intensive care, epidemiology, and data science experts from multiple regions (including low-resource settings); real-world analyses from low- and middle-income countries with a wide geographic distribution, supporting generalizability (prior SOFA-1 validation used far fewer patients); and collaboration via multiple modified Delphi rounds and data analyses, yielding an evidence-based bedside tool applicable across ICUs.

To support broader applicability, the team developed guidelines for hospitals that serve socially vulnerable populations and settings with limited access to diagnostic tests or advanced therapies. A SOFA score of 2 is not routinely used in clinical settings. “It is still too early to say that it is in use. It is gaining a lot of attention, and soon we should begin to see applications,” Ranzani said.

How the Tool Works

The structure of the SOFA scoring system remained the same. It remains a practical, low-cost bedside tool designed for daily use that does not require additional laboratory testing beyond standard ICU monitoring.

Assessment relies on the information available at the time of evaluation, such as whether a patient is receiving dialysis or is in a coma, oxygenation status, and platelet count. Each of the six organ systems was scored from 0 to 4. Scores of 1-2 indicate organ dysfunction, and scores of 3-4 indicate organ failure. Scores were summed up to a maximum of 24, with higher scores reflecting greater organ dysfunction and illness severity.

Key Differences Between SOFA 1 and SOFA 2

SOFA-2 modified the cutoff values for the six organ systems of the original SOFA score, particularly brain, respiratory, cardiovascular, liver, kidney, and hemostasis, reflecting advances in treatment options and clinical practice.

Noninvasive respiratory support, including high-flow nasal cannulas and noninvasive ventilation via facial or nasal masks, has now been incorporated into respiratory assessments.

In contrast, a SOFA score of 1 point accounted only for invasive mechanical ventilation. Updated criteria were also introduced for vasoactive medications used to stabilize blood pressure.

“The higher the dose, the more severe the patient’s condition. At that time, the medications and doses were inconsistent with the current protocols. We have also updated this,” Ranzani stated.

Another key advancement is the improved applicability of the model to ICUs with limited resources.

“We provide many indications on how to manage and score patients,” he said. “Previously, it was unclear how to respond to certain situations. Now, we have very direct recommendations, he said. This includes guidance when diagnostic tests and treatments are unavailable.

“To assess the lungs, we can draw blood from the artery in the hand, but we do not measure this in all patients. The study proposed the use of pulse oximetry saturation,” Ranzani noted.

He added that the revised score also addressed limited access to renal replacement therapy. “We provide guidance on what to do if a physician practices in a country without access to dialysis machines. Based on blood biochemistry, we established criteria indicating equivalence to dialysis. Previously, dialysis was not considered in the scoring system. Now it counts for the maximum score, and when dialysis would be indicated but is unavailable, that also counts as 4 points.”

Efforts to formally define gastrointestinal and immunologic dysfunction have not reached a consensus because of limited data and a lack of validation. “We recommend that validation efforts be undertaken to better characterize these types of dysfunctions, which can occur in the ICU and are not quantified,” Ranzani said.

Expert Reaction and Next Steps

According to the authors, the need to update SOFA-1 has long been recognized by intensive care physicians and clinical researchers, as years without revisions have caused ambiguities in interpretation, leading to inconsistent scoring.

Fernando Suparregui Dias, MD, PhD, coordinator of the intensive care service at Hospital São Lucas, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil, agreed that revision was overdue.

“This update was necessary because, over three decades, there have been significant changes in the approach to critically ill patients, with the introduction of new drugs and technologies, such as extracorporeal membrane oxygenation and other forms of extracorporeal circulatory support. This influences how we treat critically ill patients.” Dias said.

Dias also highlighted the validation using databases comprising millions of ICU admissions. “From an epidemiologic standpoint, this is extremely powerful to support clinical practice and provides a very accurate view of the degree of patient impairment,” he said.

They added that SOFA 2 could replace SOFA 1 in the coming years, depending on factors such as the heterogeneity of each population in the ICU and patient turnover rate. As noted in this study, clinicians are likely to apply both scores in parallel during the initial transition period before fully adopting the revised tools.

Further research is planned to evaluate SOFA 2 scores in pediatric populations and critically ill patients outside the ICU, including in emergency departments and semi-ICUs.

Both require validation of their applicability and efficacy, as with SOFA 1, which was adapted for children after the score was introduced in adults.

“We believe the new score will need adaptation, because children have specific physiology that changes greatly with age,” Ranzani said. “We used ICU data, but critically ill patients are also treated outside the ICU, including in emergency departments, hospital wards, and step-down units. The score will probably apply well to these settings, but it needs to be validated,” he concluded.

Sarah Alves Moura is a journalist with 5 years of experience covering health. She has collaborated with outlets such as VivaBem, the health and wellness platform of Universo Online, one of Brazil’s largest online news portals; Época Negócios, a Brazilian business magazine; and Band (Rede Bandeirantes), a Brazilian television network. In 2022, she joined Folha de S. Paulo — one of Brazil’s leading newspapers — as a trainee in its Science and Health program.

This story was translated from Medscape’s Portuguese edition.