What to know
- There are 4 types of National Death Index (NDI) searches.
- Every search type returns the date of death, state of death, and death certificate number for all matches. NDI Plus searches also return the cause of death.
- NDI users should submit as much information as possible about each study subject when requesting data.
Search types
There are 4 types of National Death Index (NDI) searches. Search costs vary by search type. Fees for the NDI Plus service are slightly higher.
Types of searches
- Researcher doesn't know if subjects are deceased
- Results provide date of death, state of death, and death certificate number
- Results do not provide any cause of death information
- Part of NDI Plus service
- Researcher doesn't know if subjects are deceased
- Results provide date of death, state of death, and death certificate number
- Results provide cause of death information in International Classification of Diseases (ICD) format
- Part of NDI Plus service
- Researcher knows all subjects are deceased
- Results provide date of death, state of death, and death certificate number
- Results provide cause of death information in ICD format
- Part of NDI Plus service
- Limited to researchers who already have information from the death certificate
- Results provide the ICD codes used to identify the cause of death on the death certificate
Search criteria
Researchers use the NDI retrieval program to search for NDI files. The program rejects any user records that don't have sufficient information about data variables used to qualify and identify a match. Detailed information about the search requirements can be found on the Eligibility Requirements page.
Search results
Requested NDI file years are searched to determine whether a particular NDI death record is a possible record match with a particular study subject record.
NDI returns the date of death, state of death, and death certificate number for all matches to the researcher. Researchers who have purchased the NDI Plus service also receive all causes of death listed on the death certificate, for all "true matches." If there is disagreement with the identified true match, the cause of death may be provided for your identified alternates. Cause of death information is provided in ICD format.
Increase your chance of matches
NDI users are encouraged to submit all information listed on the Eligibility Requirements page. Sending only the minimal criteria needed for a match could identify many matches for each record you submit. To identify a "true match," you should provide as much of the information listed in Exhibit 1 in the NDI User's Guide as available.
The file years included in the search request are the years you identified on the Transmittal Form. Only those years will be searched for potential matches for your records.
NDI Plus service
The NDI Plus service provides cause of death information at an additional cost to the researcher. These data are provided only for "true matches," not all matches. A true match is the one that is likely to be correct for a given subject.
Cause of death information is provided as permitted by the laws governing the jurisdiction of death.