Contents of the NHANES-CMS Linked Data Files

The linked Medicare data are organized into three groups: Master Beneficiary Summary File (MBSF), fee-for-service claims data files, and other files.

Background

The NCHS-CMS linked Medicare files are organized at the person-level, claim-level, or stay-level (i.e., for the inpatient and skilled nursing facilities [SNF] Medicare Provider Analysis and Review [MedPAR] files). A claim is a request for reimbursement that providers submit to insurance companies for services rendered. It includes the description of services and diagnoses. A ‘stay’ represents all services provided to a beneficiary from the date of admission to a facility through the discharge date. Some researchers are interested in totaling charges or payments up to various levels of aggregations, such as single stays or episodes of care that could continue over many months or an entire year. The unit of analysis is listed as a bullet point at the end of each of the following paragraphs.

Master Beneficiary Summary File

The Master Beneficiary Summary File (MBSF) is an annual file containing demographic and enrollment information about beneficiaries enrolled in Medicare during each calendar year. It does not contain information on all beneficiaries ever entitled to Medicare, only those enrolled during the calendar year. The MBSF can be used to determine beneficiary demographic characteristics, entitlement, and beneficiary enrollment in various Medicare programs. The MBSF consists of several segments as noted below. Each segment is provided as a separate data file.

The Base (A/B) segment includes beneficiary enrollment information, such as monthly entitlement indicators, reasons for entitlement (initial and current), and monthly enrollment indicators for Medicare Parts A and B (Medicare fee-for-service) or Medicare Part C (Medicare Advantage). The Part D segment includes variables specific to Medicare Part D Prescription Drug plan enrollment. The Cost and Utilization segment includes summarized information about the service utilization and Medicare payment amounts by type of claim for Medicare fee-for-service enrolled beneficiaries and includes summarized cost and utilization information for Medicare Part D Prescription Drug enrollees. The Chronic Conditions segment includes variables that indicate a Medicare fee-for-service enrolled beneficiary has received a service or treatment for selected chronic health conditions. Those conditions are listed in the NCHS-CMS Medicare Data Linkage Methodology and Analytic Considerationspdf icon.

• Unit of Analysis: Each record represents a unique Medicare beneficiary for a given Medicare enrollment year.

Medicare Fee-for-Service Claims Files

A claim is a request for reimbursement that providers submit to insurance companies for services rendered. It includes the description of services and diagnoses. A ‘stay’ represents all services provided to a beneficiary from the date of admission to a facility through the discharge date. All Medicare claims data files contain standard format extracts of research-oriented Medicare program data. Medicare fee-for-service claims data contain final action health care claim data submitted for payment to Medicare by institutional and non-institutional providers.  A final action health care claim contains all payment adjustments between Medicare and providers and represents Medicare’s final payment action for each health care claim. Claims for non-covered services or other non-paid claims are not included.

The Medicare Provider and Analysis Review (MedPAR) File contains inpatient hospital and skilled nursing facility (SNF) stays that were covered by fee-for-service Medicare. MedPAR records are created by rolling up individual inpatient and SNF fee-for-service final action claim records into a single inpatient or SNF stay record. All Medicare Part A short and long stay hospitalization claims and SNF claims for each calendar year are eligible for inclusion on the MedPAR file. Inclusion of hospital stay claim records on the MedPAR file are based on year of discharge. SNF claims are included based on year of admission into the facility. The file includes dates of service, ICD-9-CM diagnoses, ICD-9-CM procedures, and reimbursement amounts associated with each hospital or SNF stay. Each MedPAR record may represent a single claim or multiple claims, depending on the length of stay and the amount of services received during the stay. There can be multiple records per person on the MedPAR file.

• Unit of Analysis: One record generally represents one inpatient or SNF stay.

The Carrier Files (formerly the Physician/Supplier Part B File) contain claims data submitted by non-institutional providers, such as physicians, physician assistants, clinical social workers, nurse practitioners, independent clinical laboratories, and standalone ambulatory surgical centers as well as durable medical equipment (DME) claims processed by carriers who also process physician claims.

• Unit of Analysis: Each record represents a unique final action Medicare claim.

The Durable Medical Equipment (DME) Claim Files contain claims processed by authorized DME suppliers. DME claim records can contain claims for medical equipment such as oxygen, walkers, and wheelchairs. Information contained in the DME file includes diagnosis codes, description of equipment, dates of service, and reimbursement amount. DME claims on the Carrier file and the DME file are for separate services and are not duplicates.

• Unit of Analysis: Each record represents a unique final action Medicare claim.

The Home Health Agency (HHA) Files contain claims data submitted by Home Health Agency (HHA) providers and include information on the number of visits, type of visit (skilled-nursing care, home health aides, physical therapy, speech therapy, occupational therapy, and medical social services), the dates of visits, and reimbursement amount.

• Unit of Analysis: Each record represents a unique final action Medicare claim.

The Hospice Files contain claims data submitted by hospice providers. Data include information on the level of hospice care received (e.g., routine home care, inpatient respite care), the dates of service, reimbursement amount, hospice provider number, and beneficiary demographic information.

• Unit of Analysis: Each record represents a unique final action Medicare claim.

The Outpatient Files contain claims data submitted by institutional outpatient providers, such as hospital outpatient departments, rural health clinics, renal dialysis facilities, comprehensive outpatient rehabilitation facilities, community mental health centers, and ambulatory surgical centers for each calendar year.

• Unit of Analysis: Each record represents a unique final action Medicare claim.

Other Files

The Part D Prescription Drug Event (PDE) File contains the utilization records for beneficiaries enrolled in the Part D Prescription Drug program. The Part D PDE file contains a summary of prescription drug costs and payment data used by CMS to administer benefits for Medicare Part D enrollees. The PDE file does not contain individual drug claims; records are summary extracts submitted to CMS by Medicare Part D prescription drug plan providers. The Part D PDE files contain one record per prescription drug event. There can be multiple records per Part D enrolled beneficiary.

• Unit of Analysis: Each record represents a prescription drug event.

Variable Lists

A full list of the variablespdf icon contained in each file is available on the NCHS website.

Information: Although the MBSF contains sex, race, and date of birth variables, NCHS recommends that you use sex, race-ethnicity and date of birth provided in NHANES.

Common Variables

In addition to the NHANES participant public identifier (variable name: SEQN), there are several other common types of variables which appear in the different Medicare data files. Examples include diagnoses associated with the visit, dates of service, provider type, charges and costs, and reasons for claim non-payment. There is also some demographic information on all files.

Warning: The Medicare data come from administrative records and there may be some inconsistencies because Medicare data are collected for administrative, not research, purposes.

Resources

• Centers for Medicare & Medicaid Services (CMS) websiteexternal icon
• Chronic Condition Data Warehouse (CCW) websiteexternal icon
• ResDAC data file descriptionexternal icon
• NCHS-CMS Medicare data file documentation
• Linked NCHS-CMS Medicare Data Linkage Methodology and Analytic Considerationspdf icon
• Linkage of NCHS Population Health Surveys to Administrative Records From Social Security Administration and Centers for Medicare & Medicaid Services
• International Classification of Disease (ICD) code

The linked Medicaid data are organized into two groups: summary files and claims files.

Background

The NCHS-CMS linked Medicaid files include enrollment and claims data for persons enrolled in Medicaid and the Children’s Health Insurance Program (CHIP). Each state collects and reports Medicaid enrollment and utilization data via the Medicaid and CHIP Statistical Information System (MSIS). The enrollment data identify Medicaid and CHIP enrollees in each month of the calendar year. The fee-for-service (FFS) claims data identify who received what service from which provider at what cost. The managed care encounter records (also known as encounter claims) identify who received what service under which managed care organization and from which provider. The MSIS data are challenging to use for research because the data represent a mixture of time periods including state specific fiscal years. Consequently, CMS developed the Medicaid Analytic Extract (MAX) files, a more research-friendly set of Medicaid administrative files which provide enrollment and claims data for a given calendar year. The enrollment information in MAX identifies monthly enrollment after the retroactive or correction eligibility adjudication has been applied. The claims in MAX identify the services rendered and the cost of those services after the final payment adjustments have been applied.

Diagram: NHANES-Medicaid Linked Data Structure

View text version of diagram

Summary Files

The Person Summary (PS) File for each year of MAX data is designed to contain one record for each beneficiary enrolled in Medicaid or the Children’s Health Insurance Program (CHIP). In some cases, as described further below, a beneficiary may have more than one record on the PS File during the same year. This might happen, for example, if a person was enrolled in Medicaid in more than one state during the same year. The PS File contains basis of eligibility, monthly enrollment data, type of coverage, demographic information, and summary information regarding expenditures and service use.

• Unit of Analysis: Each record represents a Medicaid beneficiary for a given Medicaid enrollment year.

Information: You should always include a request for the Person Summary (PS) File as part of your data request. Although the PS File contains sex, race, and date of birth variables, NCHS recommends that you use sex, race-ethnicity and date of birth provided by NHANES.

Claims Files

The Inpatient Hospital (IP) File for each year of MAX data contains complete stay records for Medicaid enrollees who used inpatient hospital services and may include more than one record per beneficiary. Records include fee-for-service (FFS) claims and encounter records submitted for stays covered by Medicaid managed care. The file includes admission and discharge dates, diagnosis-related groups (DRG), Medicaid payment for fee-for-service records, third-party payments, Medicaid-paid Medicare copayment and deductible amounts, up to nine ICD–9–CM diagnosis codes, and principal and additional procedure codes.

• Unit of Analysis:   Each record represents an inpatient stay.

The Other Services (OT) File for each year of MAX data contains two major types of records: 1) records for all non-institutional services delivered that are not reported in other files and 2) payment records for premiums paid to the following types of Medicaid managed care plans: HMOs, health insurance organizations, prepaid health plans (PHPs), and primary care case management plans (PCCMs). There may be more than one record per beneficiary on this file. The service types in the OT File include physician and professional services, outpatient and clinic services, DME, hospice, home health care, and laboratory and X-ray. Information in the OT Files includes dates and types of service, Medicaid payment for fee-for-service enrollees, third-party payments, Medicaid-paid Medicare copayment and deductible amounts, a procedure code, and up to two ICD–9–CM diagnosis codes.

• Unit of Analysis: Each record represents a unique claim for service or Medicaid payment.

The Long Term Care (LT) File for each year of MAX data includes institutional long-term care records for services provided by four types of long-term care facilities: mental hospitals for the aged, inpatient psychiatric facilities for persons under age 21, intermediate care facilities for the mentally disabled, and nursing facilities (NF). Records include fee-for-service (FFS) claims and encounter records submitted for stays covered by Medicaid managed care. There may be more than one record per beneficiary on this file. Information in the LT File includes start and end dates of services, patient status at discharge, Medicaid payment amounts for fee-for-service records, third-party payments, Medicaid-paid Medicare copayment and deductible amounts, and up to five ICD–9–CM diagnosis codes. These records do not include procedure codes. Other community-based LTC services (e.g., many home-based and personal care services) are included in the OT File.

• Unit of Analysis: Each record represents a unique claim or encounter.

The Prescription Drug (RX) File for each year of MAX data contains prescribed drugs, over-the-counter drugs, and other items dispensed by a freestanding pharmacy (nonhospital-based) and may include more than one record per beneficiary. Information in the RX File includes prescription fill date, new or refill indicator, National Drug Code, and quantity and day supply. Also included are payment amounts, third-party payments, and Medicaid-paid Medicare copayment and deductible amounts.

• Unit of Analysis: Each record represents a unique claim.

Variable Lists and Record Layouts

A full list of the variablespdf icon for the NCHS-CMS Medicaid files is available on the NCHS website.

Common Variables

In addition to the NHANES participant public use ID (variable name: SEQN), there are several other common types of variables which appear in the different Medicaid data files. Examples include diagnoses associated with the visit, dates of service, provider type, charges and costs. There is also some demographic information on all files.

Warning: The Medicaid data come from administrative records and there may be some inconsistencies because Medicaid data are collected for administrative, not research purposes.

Resources

• Centers for Medicare & Medicaid Services (CMS) websiteexternal icon
• Medicaid Analytic eXtract (MAX) General Informationexternal icon
• Chronic Condition Data Warehouse (CCW) websiteexternal icon
• ResDAC data file descriptionexternal icon
• NCHS-CMS Medicaid data file documentation
• Linked NCHS-CMS Medicaid Data Linkage Methodology and Analytic Considerations
• Linkage of NCHS Population Health Surveys to Administrative Records From Social Security Administration and Centers for Medicare & Medicaid Servicespdf icon
• International Classification of Disease (ICD) code

Continuous National Health and Nutrition Examination Survey (NHANES) data for years 1999-2012 have been linked with enrollment and fee-for-service (FFS) claims data from the Centers for Medicare & Medicaid Services (CMS).