Task 1: How the NHANES data are linked to Medicaid enrollment and claims data

The survey respondents who were considered linkage eligible and were sent to CMS to match to the Medicaid Statistical Information System (MSIS) for the specific years of interest. The range of years of NHANES and Medicaid data that are linked are described in Course 1, Module 3, Task 2 “NHANES-CMS Linked Data Years of Availability”. The file used for matching did not contain the NHANES participants’ public-use ID.

NHANES linkage eligible respondents were linked with their Medicaid data using the following individual identifiers:

• Social Security Number (SSN),
• Date of birth (month and year), and
• Sex

To be considered a successful match, the NHANES respondent’s record needed to match exactly to the MSIS for all three items listed above. CMS extracted data from each of the Medicaid files for the specific years of linkage for those records that were successfully matched to the continuous NHANES respondents.  

It should be noted that survey participants who died in the time frame between the survey and the linkage interval were eligible for linkage if they had sufficient personally identifiable information and had not refused to provide their SSN or HIC number. Non-matches include participants eligible for linkage that were not enrolled in Medicaid, as well as those not successfully matched to the MSIS for the specific years.

A more thorough discussion on the linkage process for Medicaid may be found in the report Linkages between Survey Data from the National Center for Health Statistics and Medicare Program Data from the Centers for Medicare and Medicaid Services. A link to the report is located in the Resources section.

Resources

Linkages between Survey Data from the National Center for Health Statistics and Medicaid Program Data from the Centers for Medicare and Medicaid Services.