Knowledgebase

ResDAC has developed over 100 articles that cover topics ranging from the CMS data request process through using the data for a study. CMS has developed additional resources, including TAF data quality briefs and TAF data quality state snapshots, examining the quality of the Medicaid data.
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Introductory
Articles
Differences between RIF, LDS, and PUF Data Files
CMS offers files from aggregate data to individual person level data. This article describes the differences between the aggregate, public use files, the limited data sets,…
Federal Regulations Governing the Release of CMS Data
This article describes the Federal Regulations that govern the release of CMS data for research.
Strengths and Limitations of CMS Administrative Data in Research
The purpose of this article is to identify 1) common strengths of Medicare and Medicaid administrative data and 2)  broad limitations for researchers to consider when…
Popular
Articles
How to Identify Hospital Claims for Emergency Room Visits in the Medicare Claims Data
This article provides guidance on how to identify hospital emergency room claims from the Medicare files.
Diagnosis and Procedure Coding Resources
Providers that bill Medicare use codes for patient diagnoses and codes for care, equipment, and medications provided. This articles provides resources to identify the codes…
CMS Cell Size Suppression Policy
To describe the CMS cell size suppression policy and provide examples of common scenarios and possible options.

Featured Article

Provider Variables in Medicare Fee-for-Service and Encounter Data
There are many different provider variables in the Medicare Fee-for-Service (FFS) Claims and Encounter data. Researchers are often interested in the performing NPI and/or the facility CCN or organizational NPI, but other variables are sometimes…
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Long Term Care Hospitals in the Medicare Data
The purpose of this article is to define a Long-Term Care Hospital (LTCH) and to identify the files that contain claims submitted by a LTCH.
A Comparison of Medicare Limited Dataset Outpatient Files
CMS offers several claim-level files that contain outpatient claims; that is, facility claims submitted for care covered under Part B. Three versions of the LDS files are described:Outpatient file,Outpatient Prospective Payment System (OPPS) file, and OPPS Partial Hospitalization file.
Medicare Carrier and Outpatient Files: Identifying Ambulance Services
Claims for ambulance services are found in both the Carrier and the Outpatient claims data. This article describes how to identify ambulance services.
CMS Risk Adjustments
With the exception of PY 2014, CMS research files do not include beneficiary risk adjustment scores.  However, CMS does provide the programming code and instructions to calculate the three risk adjustments that CMS uses as the basis for managed care payment. 
Medicare MedPAR, Inpatient, Outpatient RIF and LDS files: “V” in the fifth position of the Provider Number
Beginning in 2008, some hospital provider numbers appearing in the claims contain a “V” in the fifth position of the six-digit Medicare Provider Number. Usually, the fifth position is a number, not a character. These hospital provider numbers appear in the MedPAR, Inpatient and Outpatient files for both RIF and LDS versions. ResDAC recommends that researchers remove these claims.
Medicare and Medicaid Statistical and Summary Data
This article provides resources for obtaining statistics and reports related to the Medicare and Medicaid programs and their beneficiaries. The following Medicare/Medicaid statistical and summary data resources address some of the most common requests for this type of information. These are by no means exhaustive.
Linking the Medicare Current Beneficiary Survey (MCBS) to Identifiable Data
Occasionally researchers need to obtain identifiable data for MCBS participants, including claims data outside MCBS participation (i.e. before or after the individual participates in the MCBS). This article provides a brief overview of that process.
Date Information in the Limited Data Set (LDS) Medicare Claims Files
This article outlines the availability of date of service information for the Limited Data Set (LDS) Medicare claims files.
RIF Medicare Quarterly Data
Researchers may request Research Identifiable File (RIF) Medicare data on a quarterly basis, in addition to the annual files. Data available on a quarterly basis includes Medicare Research Identifiable FFS claims (Inpatient, Outpatient, Home Health Agency, Hospice, Skilled Nursing Facility, Carrier, and Durable Medical Equipment) and the Master Beneficiary Summary File: Base A/B segment.
Medicare Limited Data Set (LDS) Quarterly Claims and Enrollment Data
CMS began offering quarterly claims and enrollment data with Quarter 3, 2015. This article describes the quarterly data file creation, availability, and pricing.
Differences between the Inpatient and MedPAR Files
Researchers who are interested in studying inpatient utilization (e.g. hospital stays) have two options: the Inpatient claims file or the Medicare Provider Analysis and Review (MedPAR) file. It is important to note that the differences between the two files will vary depending on whether a researcher is interested in the Research Identifiable File (RIF) or Limited Data Set (LDS) versions of the two files.
Medicare Inpatient File, LDS or RIF: Counting Distinct Hospitalizations
Hospitals may submit multiple claims for some hospitalizations. This article provides guidance for counting distinct inpatient hospitalizations and for sequencing claims for each distinct hospitalization found in the Inpatient Research Identifiable File (RIF) and Limited Data Set (LDS) files. This guidance is not applicable to the MedPAR because each record in that file is already a distinct hospitalization.