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 Soci al Security Administration for a cohort Df breast cancer patients. Only the National Death Index allowed follow-up for subjects with an unknown Social Security number. All of the deaths identified by the Social Security Admin istration were reported by the National Death Index. No subject reported to be alive by the Social Security Administration matched a National Death In dex record. Subjects with inaccurate identifying information were more effe ctively followed up by the National Death Index. The National Death Index m ore accurately reported dates of death.