National Center for Health Statistics

Concordance Between Self-Report of Medicaid 

Enrollment in the National Health Interview Survey 

and Medicaid Administrative Records

Jessie L. Parker, Health Statistician, Data Linkage Program

Data Linkage Methodology and Analysis Branch

Division of Analysis and Epidemiology

Co-author: Crescent B. Martin, Data Linkage Program

FCSM Research & Policy Conference

October 27, 2022
Background and outline

 Linking data sources expands the analytic utility of population and provider surveys

 The National Center for Health Statistics (NCHS) recently completed the first linkage 

with Transformed Medicaid Statistical Information System (T-MSIS) administrative 

data from the Centers for Medicare and Medicare Services (CMS)

 This presentation will cover: 

– The NCHS Data Linkage Program

– Medicaid and CHIP (Children’s Health Insurance Program) reporting in the 

National Health Interview Survey (NHIS)

– The NHIS-CMS T-MSIS data linkage

– Concordance of survey and administrative reporting of Medicaid/CHIP coverage

– How to access NCHS linked data
NCHS Data Linkage Program: Overview

 Create linked data files that support high quality research and program 

evaluation 

 Utilize state of the art linkage methodologies and provide documentation 

and support for analyzing linked data files

 Explore innovative methods for maintaining researcher access to linked 

data
NCHS Survey Data

Population-based 

household surveys

National healthcare surveys

Receipt/type of housing 

assistance

Housing and Urban 

Development

Cause of death from 

National Death Index

Mortality

Medicare and Medicaid 

Healthcare utilization and 

expenditures

Geocoded 

Addresses 

Add contextual 

information to standard 

Census geocoded areas

Service records and 

benefit utilization

Department of 

Veterans Affairs

Examine factors 

associated with ESRD

NCHS linked End Stage Renal Disease

data 

Today’s focus
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Research question

 What is the concordance of Medicaid enrollment as reported in NHIS 

compared to linked T-MSIS data?

 How does this vary by age group?
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Background: Medicaid reporting in survey data

 The Medicaid undercount in survey research is well-established 

 Previous studies have found Medicaid misreporting ranges from 10-30 percent

 Linked data provides a unique opportunity to assess Medicaid undercount at 

the person-level

– Earlier work assessed concordance when linking NHIS report of Medicaid 

coverage to previous Medicaid administrative files 

– This is the first study of the Medicaid undercount using the newly linked NHISCMS T-MSIS data
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NCHS survey data linked to CMS T-MSIS data

 First linkage of NCHS survey data to T-MSIS data 

 T-MSIS replaces and improves Medicaid Analytic eXtract (MAX)

• Broader set of beneficiaries

• More claim types and claim lines

• More information on beneficiary demographics, enrollment, benefits

 NCHS surveys included in recent linkage with 2014-2019 T-MSIS data:

– 1994-2018 National Health Interview Survey 

– 1999-2018 National Health and Nutrition Examination Survey (NHANES) and NHANES III 

(1988-1994)

– 2004 National Nursing Home Survey 

– 2016 National Hospital Care Survey *linked 2015-2017 T-MSIS only
NHIS-CMS T-MSIS data linkage

Person-level survey data

Healthcare 

utilization and 

expenditures
National Health Interview Survey (NHIS)

 NHIS is a nationally representative, cross-sectional sample of the US civilian 

noninstitutionalized population

 NHIS household interview is important source of information on nation’s health

 Type of health care coverage is assessed for each individual in household

 Parents are proxy responders for children

 If no coverage is reported and the survey participant is under 65, additional 

Medicaid probe is asked that provides name of state program (below)
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Medicaid administrative data: T-MSIS Analytic Files

Match Status file: identifies which survey participants were 

eligible for linkage and linked to T-MSIS

Demographic and Eligibility (DE) file: Medicaid or Children’s 

Health Insurance Program (CHIP) enrollment, including enrollment 

periods, eligibility, managed care enrollment, and more

Claims files: Inpatient, Long-Term Care, Pharmacy, and Other 

Services, includes billing information on prescription drugs, 

supplies, and healthcare services
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Analytic 

Sample

Pooled 2016-2018 NHIS linked to 2016-2018 T-MSIS

Sample Adults (SA) and Sample Children (SC) 

(n=113,408)

Linkage-eligible SA + SC 

(n=98,262)

Linkage-eligible SA + SC 

excluding 17-year-olds 

(n=96,690)

Linkage-eligible SA + SC 

excluding 17-year-olds and 

restricted benefit beneficiaries 

(n=94,789)

17-year-olds

(n=1,572)

Restricted benefit 

beneficiaries 

(n=1,901)
Approach to assessing concordance

 Analysis: explore concordance of NHIS report of Medicaid enrollment and 

linked T-MSIS administrative data

– Concordance defined as agreement between T-MSIS and NHIS in same 

month and year of survey interview

– Medicaid/CHIP enrollment was defined using the monthly CHIP_CD and 

ELGBLTY_GRP_CD variables

– Calculated overall percent agreement, sensitivity, specificity, positive 

predictive value, negative predictive value (unweighted)

– Examined overall population, as well as by age groups:

• Under 17 years old

• 18-64 years old

• 65+ years old
Results: Overall

Table 1. Comparison of National Health Interview Survey report to T-MSIS record of Medicaid/CHIP coverage, 

2016-2018*

T-MSIS record of full-scope or comprehensive 

Medicaid/CHIP coverage in same month of NHIS interview

NHIS report of Medicaid/CHIP coverage Yes No Total

Yes 14,177 2,187 16,364 

No 4,216 74,209 78,425 

Total 18,393 76,396 94,789 

Overall agreement: 93.2%

Sensitivity: 77.1%

Specificity: 97.1%

Positive predictive value: 86.6%

Negative predictive value: 94.6%

NOTES: NHIS is National Health Interview Survey. T-MSIS is Transformed Medicaid Statistical Information System. 

SOURCE: Linked National Health Interview Survey and CMS Medicaid data

*Results do not include 17-year-olds
Results: Overall

Table 1. Comparison of National Health Interview Survey report to T-MSIS record of Medicaid/CHIP coverage, 

2016-2018*

T-MSIS record of full-scope or comprehensive 

Medicaid/CHIP coverage in same month of NHIS interview

NHIS report of Medicaid/CHIP coverage Yes No Total

Yes 14,177 2,187 16,364 

No 4,216 74,209 78,425 

Total 18,393 76,396 94,789 

Overall agreement: 93.2%

Sensitivity: 77.1%

Specificity: 97.1%

Positive predictive value: 86.6%

Negative predictive value: 94.6%

NOTES: NHIS is National Health Interview Survey. T-MSIS is Transformed Medicaid Statistical Information System. 

SOURCE: Linked National Health Interview Survey and CMS Medicaid data

*Results do not include 17-year-olds
Results: Under 17

Table 2. Comparison of National Health Interview Survey report to T-MSIS record of Medicaid/CHIP coverage, 

2016-2018, Under 17

T-MSIS record of full-scope or comprehensive 

Medicaid/CHIP coverage in same month of NHIS interview

NHIS report of Medicaid/CHIP coverage Yes No Total

Yes 7,033 929 7,962 

No 1,645 12,621 14,266 

Total 8,678 13,550 22,228 

Overall agreement: 88.4%

Sensitivity: 81.0%

Specificity: 93.1%

Positive predictive value: 88.3%

Negative predictive value: 88.5%

NOTES: NHIS is National Health Interview Survey. T-MSIS is Transformed Medicaid Statistical Information System. 

SOURCE: Linked National Health Interview Survey and CMS Medicaid data
Results: 18-64

Table 3. Comparison of National Health Interview Survey report to T-MSIS record of Medicaid/CHIP coverage, 

2016-2018, 18-64 years old

T-MSIS record of full-scope or comprehensive 

Medicaid/CHIP coverage in same month of NHIS interview

NHIS report of Medicaid/CHIP coverage Yes No Total

Yes 6,004 949 6,953 

No 2,046 44,162 46,208 

Total 8,050 45,111 53,161 

Overall agreement: 94.4%

Sensitivity: 74.6%

Specificity: 97.9%

Positive predictive value: 86.4%

Negative predictive value: 95.6%

NOTES: NHIS is National Health Interview Survey. T-MSIS is Transformed Medicaid Statistical Information System. 

SOURCE: Linked National Health Interview Survey and CMS Medicaid data
Results: 65+

Table 4. Comparison of National Health Interview Survey report to T-MSIS record of Medicaid/CHIP coverage, 

2016-2018, 65 years or older

T-MSIS record of full-scope or comprehensive 

Medicaid/CHIP coverage in same month of NHIS interview

NHIS report of Medicaid/CHIP coverage Yes No Total

Yes 1,140 309 1,449 

No 525 17,426 17,951 

Total 1,665 17,735 19,400 

Overall agreement: 95.7%

Sensitivity: 68.5%

Specificity: 98.3%

Positive predictive value: 78.7%

Negative predictive value: 97.1%

NOTES: NHIS is National Health Interview Survey. T-MSIS is Transformed Medicaid Statistical Information System. 

SOURCE: Linked National Health Interview Survey and CMS Medicaid data
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Conclusions

 Among NHIS participants, there is evidence for a Medicaid undercount

– Varies by age group, from 19% for those under 17 to 31.5% for 65+

 Using linked NHIS-CMS T-MSIS data increases analytic utility of the survey 

data by supplementing the survey data with additional Medicaid and CHIP 

beneficiaries that may have been missed with survey report alone 

 Assessing concordance can help inform public health researchers and 

survey methodologists in design decisions

 Augmenting survey data with linked administrative data can help provide a 

more complete picture of health care utilization and expenditures
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Augmenting survey data with other administrative sources

0 5 10 15 20 25 30 35

Linked VA**

Linked HUD*

Linked Medicare

Linked Medicaid

Linked mortality Up to 33 years

Up to 25 years

Up to 24 years

Up to 15 years

Up to 20 years

*HUD, Department of Housing and Urban Development; **VA, Department of Veteran Affairs
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How to access restricted-use NCHS linked data

 Linked data are available through the NCHS Research Data Center (RDC) 

and Federal Statistical RDCs managed by the Census Bureau

https://www.cdc.gov/rdc/index.htm

Email: rdca@cdc.gov
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NCHS Data Linkage Program

Subscribe to the NCHS Data Linkage Program LISTSERV to receive updates! Email a message to 

list@cdc.gov. Leave the subject line blank. In the body of the message, type: 

– SUBSCRIBE NCHS-DATA-LINKAGE-PROGRAM lastname, firstname

Contact me at: Jessie.Parker@cdc.hhs.gov

Contact the Data Linkage Program: datalinkage@cdc.gov

Visit our website: www.cdc.gov/nchs/data-linkage

Thank you to Lisa Mirel and Roberto del Pozzo in the Data Linkage Program for their 

contributions and support of this work!
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References

1. Research Project to Understand the Medicaid Undercount. Phase IV Research Results: Estimating the Medicaid Undercount in the National Health 

Interview Survey (NHIS) and Comparing False-Negative Medicaid Reporting in NHIS to the Current Population Survey (CPS). 2009. Available from: 

https://www.shadac.org/sites/default/files/publications/SNACC_Phase_IV_Full_Report.pdf

2. Call K, Davern M, Klerman J, Lynch V. Comparing errors in Medicaid reporting across surveys: evidence to date. Health Serv Res. 2013;48(2pt1):652–

664

3. Davern M, Klerman JA, Baugh DK, Call KT, Greenberg GD. An examination of the Medicaid undercount in the current population survey: preliminary 

results from record linking. Health Serv Res. 2009 Jun;44(3):965-87

4. Noon JM, Fernandez LE, Porter SR. Response error and the Medicaid undercount in the current population survey. Health Serv Res. 2019 Feb;54(1):34-

43. doi: 10.1111/1475-6773.13058. Epub 2018 Oct 1. PMID: 30270431; PMCID: PMC6338296.

5. Pascale, Joanne, Fertig, Angela and Call, Kathleen. "Validation of Two Federal Health Insurance Survey Modules After Affordable Care Act 

Implementation" Journal of Official Statistics, vol.35, no.2, 2019, pp.409-460. https://doi.org/10.2478/jos-2019-0019

6. Michael Davern, Kathleen Thiede Call, Jeanette Ziegenfuss, Gestur Davidson, Timothy J. Beebe, Lynn Blewett, Validating Health Insurance Coverage 

Survey Estimates: A Comparison of Self-Reported Coverage and Administrative Data Records, Public Opinion Quarterly, Volume 72, Issue 2, Summer 

2008, Pages 241–259, https://doi.org/10.1093/poq/nfn013

7. Call K, Davern M, Klerman J, Lynch V. Comparing errors in Medicaid reporting across surveys: evidence to date. Health Serv Res. 2013;48(2pt1):652–

664

8. Research Project to Understand the Medicaid Undercount. Phase II Research Results: Examining Discrepancies between the National Medicaid 

Statistical Information System (MSIS) and the Current Population Survey (CPS) Annual Social and Economic Supplement (ASEC). 2007. Available from: 

https://www.shadac.org/

9. Call, K. T., M. Davern, and L. A. Blewett. 2007. “Estimates of Health Insurance Coverage: Comparing State Surveys with the Current Population Survey.” 

Health Affairs 26 (1): 269-78

10. Pascale, Joanne and Roemer, Marc I. and Resnick, Dean Michael, Medicaid Underreporting in the CPS: Results from a Record Check Study (Fall 2009). 

Public Opinion Quarterly, Vol. 73, Issue 3, pp. 497-520, 2009, Available at SSRN: https://ssrn.com/abstract=1468218 or http://dx.doi.org/nfp028

11. Mirel, L.B., et al., Concordance between survey report of Medicaid enrollment and linked Medicaid administrative records in two national studies. Natl 

Health Stat Report, 2014(72): p. 1-9
Appendix: Estimated linkage error rates

 Type I (false positive) and Type II (false negative) errors were 

calculated using the truth source in order to assess quality of 

matches developed

 Results: Highly accurate linkage results (low type I and type II errors)

– Deterministic matches represent the majority of total matches

– Assume a zero-error rate with deterministic approach
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For more information, contact CDC

1-800-CDC-INFO (232-4636)

TTY: 1-888-232-6348 www.cdc.gov

The findings and conclusions in this report are those of the authors and do not necessarily represent the 

official position of the Centers for Disease Control and Prevention.