Evaluation of the adequacy of vital status follow-up in the Hanford worker mortality study.

摘要

The purpose of the study described in this report was to evaluate the completeness of vital status ascertainment in the Hanford worker cohort. Identifying information on 17,708 Hanford workers, including all workers who were monitored for external radiation exposure, employed at least six months at the Hanford site, and whose vital status remains unknown, was submitted to a private search organization, Equifax Government and Special Systems. Equifax then linked Social Security numbers of these workers with death information files. For the period 1945--86 that has been emphasized in recent dose-response analyses of the Hanford data, Equifax ascertained only 12 new deaths, an increase of only 0.2% over deaths that had been ascertained previously. In addition, Equifax ascertained 23 deaths that were judged to be mismatches based on comparison of names and birth-dates on their files and ours; it is shown that this number can be regarded as a rough estimate of the number of deaths missed because workers had incorrect Social Security numbers. Overall the study suggests that the number of deaths missed was not large, but the confidence one can place in this conclusion is limited by the fact that Equifax's ascertainment procedures are not perfect, especially for the period before 1965. In order to evaluate the adequacy of the methods used by Equifax, information on 2,254 Hanford workers who had been previously identified as dead was also submitted. Equifax missed less than 2% of known Hanford deaths occurring in the period 1965--86, but missed about 18% of deaths occurring before 1965. Although recent analyses have focused on the period 1945--86, some analyses have included deaths ascertained using direct linkage with Washington state death files for the period 1987--89.