Epidemiology
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Comparative Study
A comparison of the National Death Index and Social Security Administration databases to ascertain vital status.
We compared vital status follow-up by the National Death Index and the Social Security Administration for a cohort of breast cancer patients. Only the National Death Index allowed follow-up for subjects with an unknown Social Security number. ⋯ Subjects with inaccurate identifying information were more effectively followed up by the National Death Index. The National Death Index more accurately reported dates of death.