Welcome to CEDAR (CEPI Evidence Discovery And Retrieval)

CEDAR is a standards-based API that supports search, access, and use of PCOR and other research findings across multiple repositories and programs within AHRQ CEPI.

Health IT developers can use CEDAR to integrate AHRQ CEPI research findings directly into their existing systems, where the findings can then be accessed and used by researchers, clinicians, policymakers, patients, and others. CEDAR optimizes the use of patient centered outcomes research and other research data by following standard guidelines for improving the Findability, Accessibility, Interoperability, and Reusability (the FAIR principles) of digital assets, providing fast and efficient access to information.

CEDAR Concept of Operations Diagram

CEDAR is publicly available for other platforms to use to discover and retrieve AHRQ evidence from multiple resources simultaneously.

On this webpage, you will be able to find more information on AHRQ CEPI, the CEDAR API, and the CEDAR Guide.


The Agency for Health Research and Quality (AHRQ) disseminates patient centered outcomes research (PCOR) findings, and other research evidence, into clinical practice through clinical decision support (CDS). The AHRQ Center for Evidence and Practice Improvement (CEPI) maintains research evidence and PCOR findings. Those repositories and programs include the Systematic Review Data Repository, the Effective Health Care Program, CDS Connect, and the U.S. Preventive Services Task Force Recommendations. AHRQ recognizes a need for these repositories to be more Findable, Accessible, Interoperable, and Reusable (the FAIR principles).

The CMS Alliance to Modernize Healthcare (the Health FFRDC), operated by The MITRE Corporation (MITRE), supports the CEPI Evidence Discovery And Retrieval (CEDAR) project towards reaching these goals. The project developed a standards-based application programming interface (API) that disseminates resources from multiple CEPI repositories through a single software-accessible endpoint, making the repositories (and the evidence they contain) more FAIR.

CEDAR enables health IT developers to integrate AHRQ CEPI research findings directly into their existing systems, where the findings can then be accessed and used by researchers, clinicians, policymakers, patients, and others. CEDAR optimizes the use of PCOR and research data by following standard guidelines for improving the FAIRness of digital assets, providing fast and efficient access to information.


CEDAR contains data about PCOR repositories and the artifacts (e.g., systematic reviews, evidence reports, decision aids) that they contain. CEDAR provides the following data about each repository:

  • name – the full name of the repository (e.g., Systematic Review Data Repository)
  • alias – a short name for the repository, often used for display purposes (e.g., SRDR)
  • home page – the URL where a repository can be found on the web
  • artifacts - a list of all of the artifacts CEDAR indexed for the repository

CEDAR provides the following data about each artifact it indexes:

  • source repository – the repository from which the artifact was imported
  • title – the title of the artifact (e.g., “Treatments for Acute Pain: A Systematic Review”)
  • description – a textual description of the artifact
  • url – the URL where the artifact can be found on the web
  • publication date – the date the artifact was published
  • status – the status of the artifact; has one of five possible values: “draft”, “active”, “archived”, "retracted", or “unknown”
  • type – the type of the artifact (e.g., Systematic Review, Clinician Summary, Decision Aid)
  • keywords – a list of keywords assigned to the artifact by the repository
  • concepts - a list of clinical concepts assigned to the artifact by CEDAR
  • doi - the Digital Object Identifier for the artifact, if available
  • strength of recommendation – the strength of recommendations contained within the artifact, if available
  • quality of evidence – the quality of evidence presented by the artifact, if available
  • change history - a list of changes to the artifact with timestamps of when CEDAR found the change

In addition to repository and artifact data, CEDAR also maintains a set of reference data including the National Library of Medicine (NLM) Unified Medical Language System (UMLS) Metathesaurus and Medical Subject Headings (MeSH). The former is used internally by CEDAR to assign concepts to artifacts based on their keywords. The latter is provided to users of CEDAR to allow navigation of artifacts by topic.


Client applications can use the CEDAR Application Programming Interface (API) to find and retrieve information about the evidence that CEDAR indexes. An API is a set of rules that describe how two systems communicate with each other. The CEDAR API allows developers to expand existing systems or create new ones that interact with CEDAR and artifacts indexed by CEDAR. CEDAR was developed as an API rather than as a website to promote flexibility in the types of use cases that CEDAR supports as well as to allow CEDAR to be more easily integrated with existing systems.


The CEDAR API uses a RESTful approach. REST, or Representational State Transfer, is an architectural style that imposes constraints on how an API functions. REST is typically implemented using internet technologies like the Hypertext Transfer Protocol (HTTP) and JavaScript Object Notation (JSON). offering a stateless request/response pattern. Statelessness helps achieve scalability and reduces API complexity.

The CEDAR API is built using the Fast Healthcare Interoperability Resources (FHIR) standard.

The fundamental building block for organizing data in FHIR is the Resource. A FHIR Resource is a well-specified way to represent a single concept, like a Patient or a Condition. The CEDAR API uses the Citation resource to represent and share information about indexed artifacts. The CEDAR API works by accepting requests that specify the artifacts of interest and responding with all matching artifacts as JSON FHIR Citations. The API supports several types of interaction:

  • Searching by Artifact text in the title or body of the artifact; CEDAR automatically includes synonyms when conducting searches by text
  • Searching by Artifact keyword as specified by the source repository
  • Searching by Concept; CEDAR maps Artifact keywords to health Concepts in vocabularies like SNOMED-CT or MeSH using the UMLS Metathesaurus
  • Searching by last updated or publication date; CEDAR allows Artifacts to be filtered by the date that CEDAR detects they have been modified or publication date
  • Searching by Artifact status; each Artifact in CEDAR can have a status of draft, active, unknown, archived, or retracted
  • Searching by Artifact publisher; searches can be scoped by the Artifact source repository
  • Retrieving the full list of repositories indexed by CEDAR
  • Navigating through the MeSH Concept hierarchy tree to find relevant Concepts for searching

A complete guide to using the CEDAR API can be found in the CEDAR API Getting Started Guide. Developers who want to experiment with the CEDAR API can leverage the CEDAR API Specification. The CEDAR API Specification uses Swagger UI, an open-source tool that allows users to visualize and interact with an API without building a client application. CEDAR can take advantage of the Swagger UI because the CEDAR API is documented using the OpenAPI specification. Up to date, comprehensive documentation is critical to API ease of use and adoption. The MITRE team has prioritized robust documentation of the CEDAR API to improve the experience of client application developers using the API.

The CEDAR Demonstration User Interface

You can explore CEDAR by trying the CEDAR Demonstration User Interface developed to demonstrate CEDAR capabilities, serve as a guide to development of future context-specific client applications, and support pilot testing activities.

Current CEDAR System Version Numbers:

Bitbucket Build
1e843f5 (v0.6.0)
5bff6b8 (v0.6.0)
2f1e5e0 (v0.6.0)