The MAX data are standardized eligibility and claims files for each state that include person-level information on every beneficiary enrolled in Medicaid during the calendar year. The MAX files are created from claims data that each state submits to CMS . Unlike other sources of Medicaid data, the MAX files are structured to reflect the use and cost of all Medicaid-funded services delivered to a beneficiary during the calendar year, regardless of the date that claims were paid. In addition, the variables in MAX are standardized to create comparable measures of service use and costs across states that may have significant variation in benefit packages and eligibility guidelines.
While MAX is the best data source available to examine state-to-state variation in Medicaid-funded services, there are several limitations to the data. To begin, claims data are subject to variation in diagnostic practices by physicians and other providers, and, for some states, ambiguity in mental health billing codes makes it difficult to determine what service is delivered. Studies that use claims data cannot measure EBPs as precisely as studies in clinical settings, and the use of claims data alone may make it difficult to evaluate the fidelity with which an EBP was delivered.
In addition, the MAX data do not include any service use that is not Medicaid-funded or any service use funded by state-only dollars. As a result, reliance solely on Medicaid claims may underestimate the number of beneficiaries who receive EBPs. Some components of certain psychosocial EBPs, such as supported employment, are not eligible for federal Medicaid matching funds under federal regulation. In addition, some IP psychiatric services that may serve as an indicator that a beneficiary should be receiving certain EBPs such as ACT may be missing from MAX.12 Finally, MAX files are derived from state administrative data systems that are used to determine eligibility and process and pay medical claims, and states vary in their ability to submit complete and reliable data to CMS . As a result, not all state Medicaid programs and beneficiaries could be included in the study. To the extent possible, the study attempted to include every state with MAX data of sufficient completeness and reliability, but not all states were included in the analysis and therefore not all Medicaid policy options that may affect the delivery of EBPs could be investigated.