Sequential Organ Failure Assessment (SOFA) Score

The assessment method explained

This score evaluates patient status based on clinical data in order to determine morality rate. It offers information about morbidity severity as well and is calculated at admission to the intensive care unit and monitored every 24 hours until the patient is discharged.

SOFA is the acronym from Sequential Organ Failure Assessment.

The variables included in the score (chosen by the European Society of Intensive Care Medicine) should be analysed in terms of the worst value recorded in the past 24 hours.

Because each of the items in the tool reflects organ function in six different systems, each individual score can be used for further monitoring:

■ Respiratory (through partial oxygen pressure or fraction of inhaled O₂);

■ Cardiovascular (checks hypo or hypertensive status through mean arterial pressure);

■ Hepatic (evaluation of liver function through bilirubin);

■ Coagulation (platelet count);

■ Renal (glomerular filtration rate checked through creatinine);

■ Neurological (level of consciousness assessment though Glasgow coma scale).

The following table introduces the number of points associated with each answer choice in the score:

SOFA had a good performance in validation studies, showing a good correlation with the degree of dysfunction or organ failure in critically ill patients.

There are other clinical assessments that can be used in the evaluation of ICU patients:

■ Acute Physiology and Chronic Health Evaluation II (APACHE II);

■ Simplified Acute Physiology Score (SAPS II).

Result interpretation

The answers for each of the six items are awarded a different number of points, suggestive of different degrees of dysfunction.

The overall SOFA score ranges between 0 and 24. Scores closer to 0 indicate a low degree of dysfunction whilst scores closer to 24 indicate a severe degree of dysfunction and a high mortality risk.

The table below introduces the association between SOFA scores and mortality risk percentages:

The score is recommended to be administered after admission to ICU but can also help with monitoring the evolution of the patient and may help stratify further negative outcome risks.

There was also observed a score trend in the first 48h after admission:

■ Patients with subsequent increase in SOFA score would have over 50% mortality risk;

■ Patients with unchanged score would have between 27 and 35% mortality risk;

■ Patients with subsequent decrease in score would have less than 27% mortality risk.

There is also a correlation between the SOFA score result and the length of ICU stay in patients with cardiovascular disease.

Original source

Vincent JL, Moreno R, Takala J, Willatts S, De Mendonça A, Bruining H, Reinhart CK, Suter PM, Thijs LG. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. On behalf of the Working Group on Sepsis-Related Problems of the European Society of Intensive Care Medicine. Intensive Care Med. 1996 Jul;22(7):707-10.

Validation

Vincent JL, de Mendonça A, Cantraine F, Moreno R, Takala J, Suter PM, Sprung CL, Colardyn F, Blecher S. Use of the SOFA score to assess the incidence of organ dysfunction/failure in intensive care units: results of a multicenter, prospective study. Working group on "sepsis-related problems" of the European Society of Intensive Care Medicine. Crit Care Med. 1998 Nov;26(11):1793-800.

Other references

1. 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 Oct 10;286(14):1754-8.

2. Cárdenas-Turanzas M, Ensor J, Wakefield C, Zhang K, Wallace SK, Price KJ, Nates JL. Cross-validation of a Sequential Organ Failure Assessment score-based model to predict mortality in patients with cancer admitted to the intensive care unit. J Crit Care. 2012 Dec;27(6):673-80.