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docs/resources/codelist_comparison_tool.md

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 # Codelist Comparison Tool
-Coming soon
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+Research projects that utilise electronic health records often require multiple codelists, across various coding terminologies, to accurately define phenotpyes and generate cohorts. Often this involves gathering established codelists which can be large and complex and may not fully align with the focus of a specific project. A carefully constructed and considered codelist is crucial to ensure research outcomes are both accurate and meaningful.
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+The Codelist Comparison Tool was developed to simplify the comparison of codelists and support the creation and curation of a refined and project-specific codelist. The tool integrates external libraries such as the <a href="https://phenotypes.healthdatagateway.org/" target="_blank">HDR UK Phenotype Library</a>, <a href="https://www.opencodelists.org/" target="_blank">OpenCodelists</a>, and user-generated datasets to enhance research workflows and generate more accurate and tailored codelists. 
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+To start using the Codelist Comparison Tool please click <a href="https://bhf-dsc-hds.shinyapps.io/codelist_tool/" target="_blank">here</a>.
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+For further information about using the Codelist Comparison Tool click here.