> For the complete documentation index, see [llms.txt](https://wiki.medicaiddatalearningnetwork.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.medicaiddatalearningnetwork.org/basics/dual-eligible-enrollees.md). # Dual-Eligible Enrollees {% hint style="info" icon="pen-to-square" %} Contributed by [Hyunjee Kim](https://www.ohsu.edu/people/hyunjee-kim-phd) () {% endhint %} ## Background Dually eligible individuals have both Medicare and Medicaid coverage. It is often necessary to link Medicare data (fee-for-service claims and/or Medicare Advantage encounter data) with Medicaid claims to understand their comorbidities and health care use. ## How to link Medicare claims and Medicaid TAF? When you request Medicare and Medicaid data, ResDAC or CCW will ask which encrypted beneficiary identifier (encryption option) you want to use. To make linkage straightforward: 1. Request the same encryption option for both Medicare and Medicaid data. If you do, the beneficiary ID will appear consistently in both files, which makes linking simple. 2. If you did not request the same encryption option, request a crosswalk. You can typically obtain a crosswalk file through ResDAC to link the identifiers across Medicare and Medicaid datasets. ## How do you identify dually eligible individuals? Both Medicare and Medicaid files have their own indicator of dually eligible individuals. In Medicare, you can use `DUAL_ELGBI_MONS`>=1 or `DUAL_STUS_CD_01`-`DUAL_STUS_CD_12` in [MBSF Base segment](https://resdac.org/cms-data/variables/months-dual-eligibility\)). In Medicaid, you can use `DUAL_ELGBL_CD_01` -`DUAL_ELGBL_CD_12` in [TAF- Demographic and Eligibility](https://resdac.org/cms-data/files/taf-de). Unfortunately, dual-eligibility indicators do not always match perfectly between Medicare and Medicaid data. You will need to decide whether to define dual eligibility using Medicare-based measures, Medicaid-based measures, or a combined approach (for example, treating someone as dual eligible if both source indicate dual status). ## Crossover claims in Medicaid TAF **What are crossover claims in TAF?** In Medicaid TAF, crossover claims are claims for dually eligible beneficiaries where Medicare is the primary payer and Medicaid pays some portion of the remaining amount, typically Medicare deductibles and/or coinsurance. **How to identify crossover claims** TAF includes a crossover indicator (`CROSSOVER_CLM_IND`). **Why crossover claims matter** Crossover claims often reflect Medicaid cost-sharing payments, not the full cost of the underlying service. Depending on your research question, you may want to exclude crossover claims or handle them separately. **Example: Double-counting utilization when crossover claims are not excluded** You want to count the number of outpatient visits among dually eligible beneficiaries and you have both Medicare and Medicaid data. * A beneficiary has one Medicare-covered outpatient visit. * In your Medicare claims, that visit appears once (Medicare is primary). * In TAF, Medicaid may have a crossover claim for the same visit because Medicaid paid the beneficiary’s Medicare deductible/coinsurance. * What goes wrong: If you do not exclude crossover claims, you may count the same visit twice (once in Medicare and once in Medicaid), inflating your outpatient visit counts. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://wiki.medicaiddatalearningnetwork.org/basics/dual-eligible-enrollees.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.