Concordance between survey report of Medicaid enrollment and linked Medicaid administrative records in two national studies.

The National Health and Nutrition Examination Survey (NHANES) and the National Health Interview Survey (NHIS) are population-based surveys that have each been linked to administrative data from the Centers for Medicare and Medicaid Services (CMS): the Medicaid Analytic eXtract (MAX) files. These linked data were used to examine, among children under age 18 years, respondent-level concordance between Medicaid or the Children's Health Insurance Program (CHIP) enrollment as reported in each survey (NHANES and NHIS) and as indicated by administrative data from the MAX files. Concordance was defined as having Medicaid/CHIP reported as a health insurance source in the survey questionnaire and having a CMS Medicaid/CHIP administrative record in the same month and year as the interview. Records were also considered concordant if there was no report of Medicaid/CHIP coverage based on the interview response and no match to the CMS administrative records for Medicaid enrollment. Between NHANES and MAX, 88% of observations were concordant with respect to Medicaid or CHIP enrollment, yielding a Kappa of 0.71. Between NHIS and MAX, 89% of observations were concordant with respect to Medicaid or CHIP enrollment, yielding a Kappa of 0.73. These concordance rates provide support for the use of both administrative and NHANES and NHIS as a valuable tool for public health researchers and survey methodologists.