Sudden Cardiac Death Reporting in US Dialysis Patients: Comparison of USRDS and National Death Index Data.

BACKGROUND Cause-specific mortality data from the United States Renal Data System (USRDS) form the basis for identifying cardiovascular disease (CVD), specifically sudden cardiac death (SCD), as the leading cause of death for patients on dialysis. Death certificate data from the National Death Index (NDI) is the epidemiological standard for assessing causes of death for the United States population. The cause of death has not been compared between the USRDS and the NDI. METHODS Among 39,507 adults starting dialysis in the US, we identified 6436 patients who died between 2003-2009. We classified the cause of death as SCD, non-SCD CVD, cancer, infection, and others; and compared the USRDS to the NDI. RESULTS Median age at the time of death was 70 years, 44% were female, and 30% were non-Hispanic Black individuals. The median time from dialysis initiation to death was 1.2 years. Most deaths occurred in-hospital (N=4681, 73%). The overall concordance in cause of death between the two national registries was 42% (κ=0.23, 95% confidence interval 0.22 to 0.24). CVD, including SCD and non-SCD CVD, accounted for 67% of deaths per the USRDS but only 52% per the NDI; this difference was mainly driven by the larger proportion of SCD in the USRDS (42%) versus the NDI (22%). Of the 2962 deaths reported as SCD by the USRDS, only 35% were also classified as SCD by the NDI. Out-of-hospital deaths were more likely to be classified as SCD in the USRDS (60%) versus the NDI (29%), compared to in-hospital deaths (41% in the USRDS; 25% in the NDI). CONCLUSIONS Significant discordance exists in the causes of death for patients on dialysis reported by the USRDS and the NDI. Our findings underscore the urgent need to integrate NDI data into the USRDS registry and enhance the accuracy of cause-of-death reporting.