Finding "Zombies" in Your Database by Confirming Vital Status.

Abstract

The Alaska Cancer Registry (ACR) conducted a study to identify and correct the vital status of certain cases in its database. These cases were reported as deceased by the original reporting health care facility but were not identified as being deceased using routine death resources. Cases incorrectly reported as deceased are referred to here as "zombies," as they are the "living dead" in the registry database. Zombie cases are problematic as they contribute toward artificially high mortality rates and artificially low survival rates. They are the opposite of "immortals," a term used in the literature to indicate cases that are alive in the registry database but are actually deceased. To start the study, ACR first linked its registry database to the state mortality database, the Social Security Death Index (SSDI), and the National Death Index (NDI). ACR has 3 non-North American Association of Central Cancer Registries (NAACCR) flag fields indicating the status of the linkage with these 3 data sources. ACR was able to identify zombie candidates by selecting deceased cases that did not successfully link with any of these 3 mortality data sources. After all 3 linkages were completed, ACR identified 20 zombie candidates out of 19,590 deceased cases. ACR researched these patients in several state-specific databases and found that 14 of them were true zombies and changed their vital status to alive. Of the remaining 6 deceased cases, 3 died out of country, 2 died in state, and 1 died out of state. ACR recommends that other state registries consider adding these 3 non-NAACCR mortality database flag fields, as they would make searching for zombie cases fairly routine. It would also serve as a way to perform a quality control check on deceased cases that accidentally become alive again after consolidation with a new facility source record.