NCHS Data Linkage

Restricted-use NCHS—CMS Medicaid MAX Data

Before 2014, the research Medicaid files were known as the Medicaid Analytic eXtract (MAX) files. These files were constructed with information from the Medicaid Statistical Information System (MSIS) from 1999 to 2012 and a combination of MSIS and Transformed Medicaid Statistical Information System (T-MSIS) data from 2014 to 2015. After 2015, the files were retired and replaced with the T-MSIS Analytic Files (TAFs).

NCHS survey data from 1999 to 2014 have been linked previously to the MAX files. The MAX files for 1999–2012 include data for enrollees in Medicaid and the Children’s Health Insurance Program in all 50 states and the District of Columbia. The availability of the data varies by MAX file type and state for 2013–2014.

The MAX data system includes a person summary (PS) file and four claims files: inpatient (IP), institutional long-term care (LT), prescription drugs (RX), and other services (OT).

Detailed descriptions of each of these files can be found in the following report: ”The Linkage of National Center for Health Statistics Survey Data to Medicaid Enrollment and Claims Data: Methodology and Analytic Considerations.”

NCHS Surveys Linked to CMS–Medicaid MAX Data

  • 1994–2013 National Health Interview Survey (NHIS)
  • 1999–2012 National Health and Nutrition Examination Survey (NHANES)
  • NHANES I Epidemiologic Follow-up Study (NHEFS)
  • Third National Health and Nutrition Examination Survey (NHANES III)
  • The Second Longitudinal Study of Aging (LSOA II)
  • 2004 National Nursing Home Survey (NNHS)
  • 2007 National Home and Hospice Care Survey (NHHCS)

Data Access

Due to confidentiality requirements, the restricted-use NCHS–CMS Medicaid data are accessible through the NCHS Research Data Center (RDC) only. All interested researchers must submit a research proposal to RDC. See the RDC website for instructions on submitting a proposal.

NCHS has created Feasibility Study Data files to assist researchers who are considering submitting an RDC application to analyze the linked NCHS–CMS Medicaid data.

See the section below on Public-use NCHS–CMS Medicaid MAX Feasibility Files for more information.

Restricted-use Data Dictionaries

Variable List

Analytic Support

Public-use NCHS–CMS Medicaid MAX Feasibility Files

To maximize the use of the restricted-use, linked NCHS–CMS Medicaid files, NCHS has created publicly available NCHS–CMS Medicaid Feasibility Study data files that can be downloaded directly from this website.

The feasibility files provide a limited set of variables that can be used to determine the maximum available sample size for each linked file. These files are especially useful to researchers considering whether to initiate an RDC proposal to analyze the restricted-use, linked NCHS–CMS Medicaid files.

Each feasibility file is specific to an NCHS survey and survey year. The following information is included in each feasibility study file:

  • NCHS survey public-use identifier
  • Survey participant eligibility status for CMS–Medicaid linkage
  • Final match status
  • Other variables indicating the specific CMS–Medicaid data files that are available for each successfully linked survey participant

Note that the feasibility study files do not contain any specific information about CMS–Medicaid benefits. Consequently, data users will need to consider external sources to approximate the number of respondents with a specific condition.

MAX Feasibility Files and Documentation