The Sequential Organ Failure Assessment (SOFA) is a morbidity severity score and mortality estimation tool developed from a large sample of ICU patients throughout the world. Unlike other scoring systems, such as the SAPS II and APACHE II systems, the SOFA was designed to focus on organ dysfunction and morbidity, with less of an emphasis on mortality prediction. The authors designed the system with an emphasis on bedside applicability and simplicity using widely available variables.
The study enrolled 1,449 patients from 40 intensive care units throughout the world during May 1995. The study excluded all patients < 13 years of age or were admitted for less than 48 hours for observation following an uncomplicated surgery.
The SOFA score is made of 6 variables, each representing an organ system. Each organ system is assigned a point value from 0 (normal) to 4 (high degree of dysfunction/failure) The worst physiological variables were collected serially every 24 hours of a patient's ICU admission. The "worst" measurement was defined as the measure that correlated to the highest number of points. The SOFA score ranges from 0 to 24.
Unlike other ICU mortality systems, SOFA was not designed to accurately predict mortality, and was originally developed examining ICU mortality (not hospital mortality). While there is no direct conversion of SOFA score to mortality, a rough estimate of mortality risk may be made based on two prospective papers that have been published.1,2 Note that this estimation is based on the maximum (highest) SOFA score during a patient's ICU stay.
Because SAPS II and APACHE II have only been validated in the first 24 hours of ICU admission, it is unknown how well each system predicts mortality following the first day of admission. In a 2001 Belgian study,2 serial SOFA scores were collected during the first 96 hours of admission. In this study, an increasing or unchanged SOFA score in the first 48-96 hours was associated with a higher mortality rate than patients with a decreasing score.
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