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CQL - Clinical Quality Language

Clinical Quality Language (CQL) is a Health Level Seven International (HL7) authoring language standard that’s intended to be human readable. It is part of the effort to harmonize standards used for electronic clinical quality measures (eCQMs) and clinical decision support (CDS). CQL provides the ability to express logic that is human readable yet structured enough for processing a query electronically. CQL is the expression logic used in Health Quality Measure Format (HQMF) beginning with the eCQMs implemented in calendar year 2019. CQL replaces the logic expressions previously defined in the Quality Data Model (QDM). Beginning with v5.3, QDM includes only the conceptual model for defining the data elements (the data model). Measure authors with access to the Measure Authoring Tool (MAT) can use the tool to author measures using CQL. Visit the MAT webpage for more information.  

CQL allows for a more modular, flexible, and robust expression of the logic. It allows logic to be shared between measures and with clinical decision support. Learn more about the advantages of CQL from the Benefits of CQL presentation.

Find the CQL Standards

The CQL standards are located on the HL7 Website: CQL Specification.

eCQM Known Issues (Standards, Tooling, and Measure Authoring) are found on the CQL Formatting and Usage Wiki.

Find the CQL-based QDM Reference

QDM versions for use with Clinical Quality Language (CQL) are found on the QDM page.

CQL Overview Resources

Explore these resources to get an overview of CQL and learn how to implement CQL from experts.

  • Learn more about the fundamentals of CQL and why it’s important for you on the CQL Educational Resources page. You will also find past presentations and webinars for the various audiences who might use CQL.
  • Watch this tutorial to see CQL in action.
  • Attend an upcoming Cooking with CQL webinar. The sessions feature open discussion from subject matter experts on the Measure Authoring Tool (MAT), show how to express measures using CQL, and review questions. Visit the eCQI Events page to find registration information.
  • Visit the CQL Qs&As page to review common questions and answers on CQL.
  • Visit the Connect page to find out how to connect to various CQL resources and register for upcoming CQL sessions.

CQL Tools for Implementers 

Access these tools to support your use of CQL.

  • GitHub Tools Repository - Find tools in support of CQL, such as the CQL-to-ELM Translator used by implementation vendors.
  • Explore the eCQI Tools & Key Resources Library for a complete list of tools and resources used with eCQMs and eCQI
  • CQL-to-ELM Translator Reference Implementation - The HL7 CQL specification defines both a high-level, author friendly syntax for expressing clinical knowledge, as well as a machine friendly, syntax-independent canonical representation of clinical knowledge called Expression Logical Model (ELM). The high-level syntax is designed to support measure and decision support authors, while the canonical representation is designed to support point-to-point sharing and machine processing applications.

CQL Resources for Authors

View these resources to learn about CQL formatting, usage, and standards.

  • CQL Formatting and Usage Wiki - Visit this wiki which serves as a collaborative workspace for the development of CQL formatting conventions and usage patterns for the representation of logic within quality measures. A selection of resources found on the wiki are
  • CQL Standard - Visit the HL7 Website to access the CQL Specification.
  • CQL Style Guide (v3) provides guidance to measure developers for authoring measure expressions and using functions, libraries and definitions for calendar year 2020 reporting. Modifications to the style guide include reference to changes in the Quality Data Model (QDM) used in eCQMs for 2020 reporting (QDM version 5.4), changes in the HL7 CQL standard and the HL7 CQL-based HQMF implementation guide (v3), and input from standards owners and measure developers to refine CQL expression. The purpose of the style guide is to standardize expression of measure concepts across eCQMs and define a uniform “look and feel” to eCQM logic using CQL. The guide focuses on a set of common best practices that have been implemented across CQL-based eCQMs in CMS quality reporting programs. The style guide also promotes the use of consistent language within the framework of CQL, including libraries, aliases, definitions, and functions, as well as guidance on other conventions, such as operator precedence. Measure stewards or developers who are developing or specifying eCQMs for future inclusion in CMS programs should align with these best practices.

CQL Archived Resources

  • CQL Style Guide (v2) aligns with the CQL expression style of eCQMs using CQL for calendar year 2019 reporting.

Introduction to CQL

Eligible Hospitals and Critical Access Hospitals

Presentations on implementing individual eCQMs with CQL are available on the eCQM Education page.

Eligible Professionals and Eligible Clinicians

Presentations on implementing individual eCQMs with CQL are available on the eCQM Education page.

  • Electronic Clinical Quality Measure (eCQM) Clinical Quality Language (CQL) Basics for Eligible Professionals and Eligible Clinicians - November 27, 2018
  • Side-by-Side Comparison of eCQM Logic Expression Using CQL Versus QDM for EPs - December 19, 2017

Measure Developers/Implementers

Cooking with CQL Sessions


Visit the CQL Q&As page to review common questions and answers on CQL.

Visit the CQL Formatting and Usage Wiki. The Wiki serves as a collaborative workspace for the development of CQL formatting conventions and usage patterns for the representation of logic within clinical quality measures. All users have edit rights to be able to submit edits, add comments and concerns. Items on the Wiki are a work in progress and subject to change. The Wiki also includes a listing of known eCQM issues (Standards, Tooling, and Measure Authoring), users can “watch” the eCQM Known Issues page to receive email notification as issues are added and updated. 

Join the CQL Technical Chat Discussion.

Participate in an upcoming HL7 CDS Workgroup call. This Work Group discusses CQL in the HL7 Clinical Quality Framework - on-Fast Healthcare Interoperability Resources (CQF-on-FHIR).

Add to or review the CQL STU comments on the HL7 website (search for CQL to view the comment page for the most current version of the standard).

Submit feedback on CQL issues, comments, and questions to the ONC Jira CQL Issue Tracker.

Last Updated: Apr 01, 2020