The Effect of Missing Data on the Measurement of Cardiac Arrest Outcomes According to Race.

INTRODUCTION

High-quality data are important to understanding racial differences in outcome following out of hospital cardiac arrest (OHCA). Previous studies have shown differences in OHCA outcomes according to both race and socioeconomic status. EMS reporting of data on race is often incomplete. We aim to determine the effect of missing data on the determination of racial differences in outcomes for OHCA patients.

METHODS

We performed a secondary analysis of a data set developed by probabilistically linking the Michigan Cardiac Arrest Registry to Enhance Survival (CARES) and the Michigan Inpatient Database (MIDB). Adult OHCA patients (age >18) who survived to hospital admission between 2014 and 2017 were included. Both datasets recorded patient race and ethnicity with CARES using a single race/ethnicity variable. Patients were categorized as White, Black, other, or missing and only a single choice was allowed. Due to the small number of Hispanic patients and the combined race/ethnicity variable, these patients were excluded. The outcomes of interest were survival to hospital discharge and survival to discharge with Cerebral Performance Category 1 or 2 (good outcome). Outcomes were stratified according to EMS- or hospital-documented race.

RESULTS

We included 3,756 matched patients, after excluding 34 Hispanic patients from analysis. Documentation of patient race was missing in 892 (22.1%) of CARES and 212 (5.6%) of MIDB patients. When both datasets documented Black or White race, agreement in race documentation was excellent (κ=0.83). White patients were more likely to have good outcomes than Black in both the CARES (27.3% vs 14.8%) and MIDB (26.9% vs 16.1%) databases (both p < 0.001), but were not more likely to survive (30.8% vs 27.3% p = 0.22; 30.3% vs 28.1%, p = 0.07). Moreover, we found no significant difference in outcome measures based on race documentation for White vs Black patients (good outcome [27.3 vs 26.9% (MIDB)] and [16.1% vs 14.8% (CARES)] respectively and survival [30.8% vs 30.3% (MIDB)] and [27.3 vs 28.1% (CARES)] respectively).

CONCLUSION

Despite higher rates of missing EMS documentation, we identified statistically similar rates in OHCA outcome measures between databases. Further work is needed to determine the true effect of missing documentation of race on OHCA outcome measures.