Relationship between functional status prior to onset of critical illness and mortality: a prospective multicentre cohort study

This prospective study aimed to assess the association between prior functional status and hospital mortality for patients admitted to four intensive care units in Spain between 2006 and 2012. Prior functional status was classified into three groups, using a modification of the Glasgow Outcome Scale (GOS), including group 1 with no limitations on activities of daily living; group 2 with some limitations but self-sufficient; and group 3 who were dependent on others for their activities of daily living. Of the 1,757 patients considered (mean Simplified Acute Physiology Score [SAPS] predicted mortality 14.8% and hospital mortality 13.7%), group 1 had the lowest observed hospital mortality (8.3%) compared to the SAPS 3 predicted mortality (11.6%). The observed mortality for group 2 (20.6%) and group 3 (27.4%) were both higher than predicted (19.2% and 21.2% respectively; odds ratio [OR] 1.97, 95% confidence interval [CI] 1.38-2.82 for group 2 and OR 2.90, 95% CI 1.78-4.72 for group 3 compared to group 1). Combining prior functional status and Sequential Organ Failure Assessment (SOFA) score with SAPS 3 further improved the ability of the SAPS 3 scores in predicting hospital mortality (area under the receiver operating characteristic curve 0.85 [95% CI 0.82-0.88] versus 0.84 [95% CI 0.81-0.87] respectively). In summary, patients with limited functional status prior to ICU admission had a higher risk of observed hospital mortality than predicted. Assessing prior functional status using a relatively simple questionnaire, such as a modified GOS, has the potential to improve the accuracy of existing prognostic models.