Medicare Current Beneficiary Survey (MCBS): Differences between the Cost and Use and Access to Care Modules

The Medicare Current Beneficiary Survey (MCBS) was released as two modules for calendar years 1991-2013. Researchers can choose to request one or both of the modules depending on their research needs. The participant records in each module can be linked using the BASEID variable. The two modules are created from the same underlying MCBS population, but there are important differences between the participants and the information contained in each module. This article is designed to provide a brief overview of the differences between the two modules.

The Access to Care is available starting in 1991 while the Cost and Use is available starting in 1992. The Access to Care module is released sooner than the Cost and Use, so the latest year of the availability will differ. The MCBS uses a rotating panel design. There are four panels active at a given time and each panel has approximately 4,000 sample participants (exact numbers will vary on the year the panel was introduced). New panels are introduced each year in the fall round and replace the oldest panel. The Access to Care module will contain four panels of participants – the new panel plus the three continuing panels. The Cost and Use module contains only the three continuing panels. The Access to Care module is designed to represent the "always enrolled" Medicare population. This means that this module will not include individuals who become enrolled after the first day of the year or individuals who disenrolled or died prior to the last day of the year. The Cost and Use module, conversely, is designed to represent the "ever enrolled" Medicare population and does not apply those exclusions. This distinction is important, particularly for those who are interested in studying mortality – the Cost and Use is the appropriate module to request for that purpose.

Both modules contain Medicare claims for participants in the module (claims are for the year of the file only – not historical or future claims). Note that there is not a claim file for the Part D data. Researchers who are interested in Part D utilization should request the Cost and Use file because it contains both prescribed medicine events that were reported by MCBS survey participants as well as Part D events that are found in the Part D administrative records. Access to Care contains Part D enrollment information and prescription medication usage that is self reported. Both modules contain information from administrative records at CMS, survey reported health status and functioning, and survey reported insurance information. Access to Care has additional survey information about participant sources of care, usual source of care and satisfaction with that care. The Access to Care also includes supplemental files, such as an HMO supplement for HMO enrollees. The Cost and Use module has event-level files for dental, facility, inpatient, institutional, medical provider, outpatient hospital, and prescribed medicine events. These event level files combine data obtained from CMS administrative records with information from the survey. This allows researchers to study health care utilization covered by payers other than traditional Medicare (fee-for-service). The Cost and Use module also includes a supplemental MDS/OASIS data file (nursing home and home health assessment data, respectively).

Researchers who would like to further compare the two modules should use the codebooks and other documentation posted on the CMS website.