Inter-rater reliability of post-arrest cerebral performance category (CPC) scores

Cerebral Performance Category (CPC) scores are often an outcome measure for post-arrest neurologic function, collected worldwide to compare performance, evaluate therapies, and formulate recommendations. At most institutions, no formal training is offered in their determination, potentially leading to misclassification.

We identified 171 patients at 2 hospitals between 5/10/2005 and 8/31/2012 with two CPC scores at hospital discharge recorded independently - in an in-house quality improvement database and as part of a national registry. Scores were abstracted retrospectively from the same electronic medical record by two separate non-clinical researchers. These scores were compared to assess inter-rater reliability and stratified based on whether the score was concordant or discordant among reviewers to determine factors related to discordance.

Thirty-nine CPC scores (22.8%) were discordant (kappa: 0.66), indicating substantial agreement. When dichotomized into "favorable" neurologic outcome (CPC 1-2)/"unfavorable" neurologic outcome (CPC 3-5), 20 (11.7%) scores were discordant (kappa: 0.70), also indicating substantial agreement. Patients discharged home (as opposed to nursing/other care facility) and patients with suspected cardiac etiology of arrest were statistically more likely to have concordant scores. For the quality improvement database, patients with discordant scores had a statistically higher median CPC score than those with concordant scores. The registry had statistically lower median CPC score (CPC 1) than the quality improvement database (CPC 2); p<0.01 for statistical significance.

CPC scores have substantial inter-rater reliability, which is reduced in patients who have worse outcomes, have a non-cardiac etiology of arrest, and are discharged to a location other than home.