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Background

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.

Differences between RIF Inpatient and RIF MedPAR

The RIF MedPAR file was specifically developed by CMS for researchers interested in studying inpatient hospital and skilled nursing facility (SNF) care. It creates a single, fixed-length record for each hospital or SNF stay. The file contains ICD diagnosis and procedure codes, admission, discharge, and procedure dates, and Diagnosis-Related Group (DRG). Information about charges for inpatient services are more highly aggregated in MedPAR than in the Inpatient file. If comfortable with sacrificing some granularity, most researchers choose the MedPAR file for studying inpatient and SNF care due to its convenient format and generally lower cost. In contrast to the Inpatient LDS and RIF, both the MedPAR LDS and RIF contain some stays covered under Medicare Advantage (MA). However, these claims will not be comprehensive, and ResDAC advises removing MA-covered claims from analyses. For more information, please see the article “Identifying Medicare Managed Care Beneficiaries from the Master Beneficiary Summary or Denominator Files.”

The Inpatient file is an alternate source of information about services provided by long stay and short stay inpatient hospitals. The Inpatient file does not contain services provided by Skilled Nursing Facilities. Claims for services provided by Skilled Nursing Facilities are found in a separate Skilled Nursing Facility (SNF) claims file. The Inpatient file contains one record per claim (less than 1% of short stays have multiple bills) and contains more detailed revenue center codes which record specific areas within a hospital involved in patient care. The Inpatient file also contains information about the attending physician, which is not available in the MedPAR. The Inpatient claims file is not as easily analyzed as the fixed-format MedPAR files and require more programming skill and manipulation. Both the RIF MedPAR and RIF Inpatient file can be linked to other RIF utilization and enrollment files using the CCW Bene ID.

Differences between LDS Inpatient and LDS MedPAR

The LDS MedPAR file is segmented into 3 data files: LDS Hospital National MedPAR, Skilled Nursing Facility MedPAR, and Long-Term Care Hospital MedPAR. The Hospital National MedPAR file was specifically developed by CMS for comment on the Inpatient Prospective Payment System. It creates a single, fixed-length record for each hospital stay. The file contains ICD diagnosis and procedure codes, admission and discharge dates (provided as a quarter/year and not an exact date of service), and DRG. Note that procedure dates are absent in the LDS MedPAR, so it is not possible to ascertain the temporal sequence of events that occurred during the stay. Information about charges for inpatient services are more highly aggregated in MedPAR than in the Inpatient claims data. The lowest level of patient geography in the LDS MedPAR is the beneficiary’s state of residence. As stated previously, in contrast to the Inpatient LDS and RIF, both the MedPAR LDS and RIF contain some stays covered under Medicare Advantage (MA). However, these claims will not be comprehensive, and ResDAC advises removing MA-covered claims from analyses. For more information, please see the article “Medicare Managed Care Enrollees and the Medicare Utilization Files.”

Arguably the most important point to understand about the LDS MedPAR is that it does not contain a unique patient identifier, so it can’t be linked with demographic information in the LDS Denominator file. Similarly, the lack of a beneficiary identifier prevents researchers from tracking multiple hospital stays for the same patient and linking to other LDS data sets at the patient level.

The LDS Inpatient file is an alternate source of information about services provided by long stay and short stay inpatient hospitals. The Inpatient file does not contain services provided by Skilled Nursing Facilities. Claims for services provided by Skilled Nursing Facilities are found in the Skilled Nursing Facility (SNF) claims files. The LDS Inpatient file contains one record per claim (less than 1% of short stays have multiple bills) and contains more detailed revenue center codes which record specific areas within a hospital involved in patient care. The LDS Inpatient file contains information about the attending physician, which is not available in the MedPAR. The lowest level of patient geography in the Inpatient LDS file is the county. The Inpatient file also contains exact dates of service starting in 2010 with an optional date file available for 2009. However, the claims files are not as easily analyzed as the fixed-format MedPAR files and require more programming skill and manipulation.

*Dates are present in the claims files as of 2010. In 2009, the dates are provided as a separate file.  Prior to 2009, the dates are presented as a Quarter and Year only.

Inpatient LDS MedPAR LDS Inpatient RIF MedPAR RIF
Beneficiary Identifier Included (Desy Sort Key) Absent Included (CCW Bene ID) Included (CCW Bene ID)
Admission/Discharge Dates Included as of CY 2010* (MM/DD/YYYY) Quarter and Year only Included Included
Procedure Dates Included as of CY 2010* Not included Included Included
Beneficiary State Included Included Included Included
Beneficiary County Included Not included Included Included
Zip Code Not included Not included Included Included
Table 1. Variable Differences Between Inpatient and MedPAR RIF and LDS Files