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CQL - 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.

Find the CQL Standards

The CQL standards are located on the HL7 Website: CQL Specification. The latest version of CQL is v1.5.1: Normative-Normative, based on Fast Healthcare Interoperability Resources® R4.

Find the CQL­-based QDM Reference

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

CQL Overview Resources

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

CQL Tools for Implementers 

Access these tools to support your use of CQL.

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 (v5) provides guidance to measure developers for authoring measure expressions and using functions, libraries and definitions for calendar year 2022 reporting. Modifications to the Style Guide include references to changes in the QDM used in eCQMs for 2021 and 2022 reporting (QDM version 5.5 Guidance Update), the HL7 CQL standard, the HL7 CQL-based Health Quality Measure Format (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 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, functions, and guidance on other conventions, such as operator precedence. Measure stewards and measure 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 (v4) aligns with the CQL expression style of eCQMs using CQL for calendar year 2021 reporting.
  • CQL Style Guide (v3) aligns with the CQL expression style of eCQMs using CQL for calendar year 2020 reporting.
  • CQL Style Guide (v2) aligns with the CQL expression style of eCQMs using CQL for calendar year 2019 reporting.

Introduction to Clinical Quality Language (CQL­)

CQL for eCQM Developers and Implementers

Get a start with CQL by visiting the CQL FAQs page to review common questions and answers.

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 electronic clinical quality measures (eCQMs). All users have edit rights to submit edits, add comments and concerns. Items on the Wiki are a work in progress and subject to change.

Join the CQL Technical Chat Discussion. (Log in or sign up for a free account.)

Participate in an upcoming Health Level Seven International® (HL7®) Clinical Decision Support (CDS) Work Group 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 Mixed Normative / Trial Use Specification 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: Nov 30, 2021