The DAC holds CMS Medicare Fee-For-Service claims data going all the way back to 1985 in support of the Dartmouth Atlas project. In the earlier years, we started out with only 20% Denominator and MedPar files (1985-1991) and 5% Carrier (1986-1997). Over time, sample sizes increased and file types expanded. By 2006, the DAC acquired approval from CMS to use 100% Medicare FFS claims to support the ongoing work of the Dartmouth Atlas and many other research projects that reuse this data. The DAC also holds Medicaid, ACO, survey, and other data used in conjunction with CMS data.
To optimize the use of CMS data for research purposes, the DAC obtains ICD-9/ICD-10 diagnosis and procedure codes, CPT/HCPCs procedures codes, DRGs, and Revenue Codes that are used by researchers to define patient condition cohorts and understand their outcomes. These codes are also used to build measures often used in statistical modeling. The DAC creates an annual publication of coding trends, which represents the number of beneficiaries and events for each code type in the CMS data.