Emergency medical services/original researchComparison of the Cerebral Performance Category Score and the Health Utilities Index for Survivors of Cardiac Arrest
Introduction
Out-of-hospital cardiac arrest is a common problem, with more than 160,000 cases occurring each year in the United States. Overall, survival to hospital discharge for out-of-hospital cardiac arrest remains poor, with survival rates, for all rhythms combined, ranging from 1% to 20%.1, 2 Variation in patient survival rates among communities can be attributed to local differences in the implementation of the chain of survival, as described by the American Heart Association.3, 4 Although survival is a key measure of resuscitation success, intact functional status is equally, if not more, germane. It has been generally believed that the best patient survival can be achieved only if all 4 of the following links have been optimized: rapid access, early cardiopulmonary resuscitation (CPR), early defibrillation, and early advanced cardiac life support. The OPALS Study, a multicenter and multiphase study, evaluated the effect of the chain of survival for 5,638 patients who experienced out-of-hospital cardiac arrest in 20 Ontario communities. The results of this work demonstrated the relative effectiveness of each of the 4 links and showed that citizen CPR and rapid defibrillation are the most important factors for survival.5, 6, 7
Health-related quality of life refers to the physical, psychological, and social domains of health as seen in domains that are influenced by a person's experiences, beliefs, expectations, and perceptions.8, 9 Several investigators have recently evaluated the outcomes or quality of life of survivors of out-of-hospital cardiac arrest.10, 11, 12, 13 We have previously found that most patients with cardiac arrest who survive to hospital discharge have good quality of life and functional status.14 We previously demonstrated that the provision of citizen CPR correlates with better functional status after out-of-hospital cardiac arrest.15
It remains an important problem for investigators to efficiently measure functional outcomes in resuscitation trials. There is no single criterion standard adopted for this purpose; however, the Cerebral Performance Category Score is widely used by investigators.16, 17, 18, 19 Though simple to use, this scoring system has not been well validated. In contrast, there are several more resource-intensive systems for evaluating functional outcomes that are seldom used, one of the most promising being the Health Utilities Index Mark 3.20, 21
The objectives of the current study were to evaluate the comparability of results from the unvalidated but easy to use Cerebral Performance Category scale versus those of the validated but more complex Health Utilities Index scale for health-related quality of life. We wished to determine the validity of using the Cerebral Performance Category scale as a replacement for the Health Utilities Index scale for assessing out-of-hospital cardiac arrest survivors. Specifically, we wished to examine (1) the typical distribution of Cerebral Performance Category and Health Utilities Index scores, (2) the ability of Cerebral Performance Category to predict or correctly classify Health Utilities Index scores, and (3) the comparability of Cerebral Performance Category and Health Utilities Index scores with regard to agreement and discrimination.
Section snippets
Study Design
This article presents a prospective cohort study of OPALS Study survivors. We have previously described in detail the methodology for the cardiac arrest and quality-of-life portions of the OPALS Study.14, 22, 23, 24 The OPALS Study incorporates a multiphase before-and-after controlled design, with the unit of study being all eligible patients with out-of-hospital cardiac arrests treated during each of the 3 distinct phases. This prospective cohort study included all survivors of out-of-hospital
Results
For the period 1994 to 2002, 8,196 eligible cardiac arrest patients representing all rhythms were treated within the OPALS Study communities (Figure 2). Of these, 418 (5.1%) patients were discharged from hospital alive and 324 (4.0%) were known to be alive at 1 year and were considered for Health Utilities Index interviews. After surviving to 1 year but before being interviewed, 1 patient died, 48 were lost to follow-up, and 7 had an incomplete survey. This left 305 patients who could be
Limitations
Our study has several potential limitations. First, the comparison of patients with moderate to severe disability was limited by the few patients who had a Cerebral Performance Category score of 2 or 3. We have, however, previously shown that most 1-year survivors of cardiac arrest experience good quality of life; thus, this is likely to represent the largest sample of such patients for some time. Second, we made several arbitrary decisions in this study. Patients were evaluated at 1 year
Discussion
With 8,196 patients and 305 1-year survivors, this represents the world's largest published study to formally evaluate the Cerebral Performance Category score against a well-validated quality-of-life measurement system, the Health Utilities Index. Overall median Cerebral Performance Category and Health Utilities Index scores in our sample were high and, specific to Health Utilities Index, similar to that of the general population score. We found that Cerebral Performance Category performed well
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Cited by (0)
Supervising editor: Theodore R. Delbridge, MD, MPH
Author contributions: IGS and LPN conceived the study, designed the trial, and obtained research funding. IGS and LPN supervised the conduct of the trial and data collection. LPN, IGS, GN, JM, JD, TB, and JB undertook recruitment of participating centers and patients and managed the data, including quality control. IGS, LPN, and GAW provided statistical advice on study design and analyzed the data. LPN drafted the article and all authors contributed substantially to its revision. IGS takes responsibility for the paper as a whole.
Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article, that might create any potential conflict of interest. See the Manuscript Submission Agreement in this issue for examples of specific conflicts covered by this statement. This study was funded by peer-reviewed grants from the Emergency Health Services Branch of the Ontario Ministry of Health and Long-Term Care and the Canadian Health Services Research Foundation. Dr. Ian Stiell holds a Distinguished Investigator Award from the Canadian Institutes of Health Research.
Publication date: Available online May 1, 2008.