OBJECTIVES

The Sequential Organ Failure Assessment and other severity of illness scales rely on the Glasgow Coma Scale to measure acute neurologic dysfunction, but the Glasgow Coma Scale is unavailable or inconsistently applied in some institutions. The objective of this study was to assess the validity of a modified Sequential Organ Failure Assessment that uses the Richmond Agitation-Sedation Scale instead of Glasgow Coma Scale.

DESIGN

Prospective cohort study.

SETTING

Medical and surgical ICUs within a large, tertiary care hospital.

PATIENTS

Critically ill medical/surgical ICU patients.

INTERVENTIONS

We calculated daily Sequential Organ Failure Assessment scores by using electronic medical record-derived data. By using bedside nurse-recorded Glasgow Coma Scale and Richmond Agitation-Sedation Scale measures, we calculated neurologic Sequential Organ Failure Assessment scores using the original Glasgow Coma Scale-based approach and a novel Richmond Agitation-Sedation Scale-based approach, converting the 10-point Richmond Agitation-Sedation Scale to a 4-point neurologic Sequential Organ Failure Assessment score. We assessed construct validity of Richmond Agitation-Sedation Scale-based Sequential Organ Failure Assessment by analyzing correlations with established severity of illness constructs (Acute Physiology and Chronic Health Evaluation II and Glasgow Coma Scale-based Sequential Organ Failure Assessment) and predictive validity by using logistic regression to determine whether Richmond Agitation-Sedation Scale-based Sequential Organ Failure Assessment predicts ICU, hospital, and 1-year mortality. We assessed discriminative performance with c-statistics.

MEASUREMENTS AND MAIN RESULTS

Among 513 patients (5,199 patient-days), Richmond Agitation-Sedation Scale-based Sequential Organ Failure Assessment was strongly correlated with Acute Physiology and Chronic Health Evaluation II acute physiology score at enrollment (r = 0.583; 95% CI, 0.518-0.642) and daily Glasgow Coma Scale-based Sequential Organ Failure Assessment scores (r = 0.963; 95% CI, 0.956-0.968). Mean Richmond Agitation-Sedation Scale-based Sequential Organ Failure Assessment scores predicted ICU mortality (areas under the curve = 0.814)-as did mean Glasgow Coma Scale-based Sequential Organ Failure Assessment (0.799)-as well as hospital and 1-year mortality. Admission Sequential Organ Failure Assessment scores, whether using Richmond Agitation-Sedation Scale or Glasgow Coma Scale, were less accurate predictors of mortality; areas under the curves for ICU mortality for Richmond Agitation-Sedation Scale-based and Glasgow Coma Scale-based Sequential Organ Failure Assessment, for example, were 0.622 and 0.608, respectively.

CONCLUSION

A modified Sequential Organ Failure Assessment score that uses bedside Richmond Agitation-Sedation Scale when Glasgow Coma Scale data are not available is a valid means of assessing daily severity of illness in the ICU and may be valuable for risk-adjustment and benchmarking purposes.