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.
Introductory
Articles
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,…
This article describes the Federal Regulations that govern the release of CMS data for 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…
Medicare-paid observation stays may be found in the Medicare Outpatient, Inpatient, or MedPAR files. This article describes how to identify observation stays that appear in each as defined by CMS billing guidance.
For data years 2006 and forward, dually eligible Medicare beneficiaries are identified in the Medicare Master Beneficiary Summary File, Base segment. Initially available only as a RIF, this file was released as an LDS file in 2016. The monthly variable “Medicare-Medicaid Dual Eligibility” identifies dual status. Dual eligibles are also identified in the Medicaid Analytic Extract (MAX) Personal Summary (PS) file.
This article has three goals: (1) to describe missing patterns on pain variables; (2) to describe the difference between real missing and skip patterns; (3) to describe which assessments should be used for calculating pain measures. This information is most relevant for researchers who work on either creating their own pain measures or constructing CMS quality measures. The new MDS 3.0 requires nursing home staff to interview residents regarding health conditions, such as pain, mood and cognitive function through…
Claims for ambulance services are found in both the Carrier and the Outpatient claims data. This article describes how to identify ambulance services.
Cost report variables are split between two data files depending on the format of the variable. A master table lists all cost report variables and the format. The “Usage” column in the master table specifies the format of the variable, which determines the file location.
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.
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.
This article provides a link and overview of the document on finder and crosswalk files written by the CMS data distributor, HealthAPT.
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.
This article provides guidance on how to identify hospital emergency room claims from the Medicare files.
This article describes the difference between two similiar variables in the carrier file -the Line NCH Payment Amount and Line Provider Payment Amount.
This article explains possible discrepancies when using the outpatient file to calculate payment amounts at the claim level and revenue center level.