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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Medicare Zip Code to Carrier Locality File
Researchers and data users who are working with CMS files may need to map zip code information to CMS carriers and localities. This article describes where to find current and historical versions of the file.
Opening the Medicare Physician/Supplier Procedure Summary Master (PSPS) File
This article provides instructions on how to open the Medicare Physician/Supplier Procedure Summary Master (PSPS) file in Microsoft Access or SAS.
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 Cost Report Data: Using Link Specifications in Microsoft Access when Importing Data
When importing Medicare cost reports into Microsoft Access, data users should use the “link specifications” option to ensure that each variable imports with the correct data type.
Medicare Cost Reports: Revised Forms and Downloadable Data
CMS updated several Medicare cost report forms. As a result, during the year of the transition and up to one year after, the facility will have two separate data downloads, one that includes all the data collected under the old form and another one under the new form. 
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.
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.
BSA Prescription Drug Event (PDE) PUF - Linking the Drug Name variable to RxNorm
Provide the steps to identify the drug name from the RxNorm database for the NDCs in the BSA PDE PUF. 
Discrepancy in the Outpatient Claim Payment Amount and Sum of the Revenue Center Payment Amounts
This article explains possible discrepancies when using the outpatient file to calculate payment amounts at the claim level and revenue center level.