Study objective: The Cerebral Performance Category score is an easy to use but unvalidated measure of functional outcome after cardiac arrest. We evaluate the comparability of results from the Cerebral Performance Category scale versus those of the validated but more complex Health Utilities Index scale for health-related quality of life.
Methods: This prospective substudy of the Ontario Prehospital Advanced Life Support (OPALS) Study included adult out-of-hospital cardiac arrest patients treated in 20 cities. This prospective cohort study included all survivors of out-of-hospital adult cardiac arrest enrolled in phase II (rapid basic life support with defibrillation) and phase III (advanced life support) of the OPALS Study, as well as the intervening run-in phase. Survivors were interviewed at 12 months for Cerebral Performance Category Score and the Health Utilities Index Mark 3 (Health Utilities Index).
Results: Of 8,196 eligible out-of-hospital cardiac arrest patients between 1995 and 2002, 418 (5.1%) survived to discharge, and 305 (3.7%) completed the Health Utilities Index interview and had Cerebral Performance Category scored at 12 months. The 305 patients had the following data: mean age 63.9 years; male 78.0%; paramedic-witnessed arrest 25.6%; bystander cardiopulmonary resuscitation 32.1%; initial rhythm ventricular fibrillation/ventricular tachycardia 86.9%, Cerebral Performance Category 1 267, Cerebral Performance Category 2 26, Cerebral Performance Category 3 12. Overall, the median scores (interquartile range) were Cerebral Performance Category 1 (1 to 1) and Health Utilities Index 0.84 (0.61 to 0.97). The Cerebral Performance Category score ruled out good quality of life (Health Utilities Index >0.80), with a sensitivity of 100% (95% confidence interval [CI] 98% to 100%) and specificity 27.1% (95% CI 20% to 35%); thus, when the Cerebral Performance Category score was 2 or 3, it was unlikely that the Health Utilities Index score would be good. The Cerebral Performance Category score had sensitivity 55.6% (95% CI 42% to 67%) and specificity 96.8% (95% CI 94% to 98%) for predicting poor quality of life (Health Utilities Index >0.40); ie, when Cerebral Performance Category was 1, it was highly unlikely that the Health Utilities Index score would be poor. The weighted kappa was 0.39 and the interclass correlation was 0.51.
Conclusion: This represents the largest study yet conducted of the performance of the Cerebral Performance Category score in 1-year survivors of out-of-hospital cardiac arrest. Overall, the Cerebral Performance Category score classified patients well for their quality of life, ruling out a good Health Utilities Index score with high sensitivity and ruling in poor Health Utilities Index score with high specificity. The Cerebral Performance Category is an important tool in that it indicates broad functional outcome categories that are useful for a number of key clinical and research applications but should not be considered a substitute for the Health Utilities Index.