Back to top
U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

What is the purpose of Quality Improvement (QI)-Core and can you explain the relationship between QI-Core, CQL, and the QDM?

The QDM is a conceptual data model that helps eCQM developers and implementers understand the general concepts needed to compute an eCQM. However, QDM only defines the concepts, such as a diagnosis, a laboratory test (with a result), or a physical examination finding (such as blood pressure readings). A method to relate each concept to other concepts requires an expression language. As an example, the QDM data element is similar to a noun in expressing grammar (e.g., a laboratory test) and related adjectives (the time the lab performed the laboratory test). But to create a sentence, one must have verbs (e.g., starts) and adverbs (after the beginning of). The expression language provides the verbs and adverbs. Prior versions of QDM (v.5.3 and earlier) included the expression language and the conceptual data model. The expression language portion of QDM was difficult to understand and more challenging to compute. CQL allows eCQM developers to better express the eCQM calculation. CQL can express that some specific activity happened during an inpatient encounter and that it happened before another activity. However, CQL needs a data model to indicate what is related to what.

  • CQL defines the expression – i.e., the relationship between item A and item B
  • QDM defines the items
  • CQL can work with other data models not just QDM. However, in the current CMS eCQM development activities, QDM is the chosen data model to work with CQL. Other projects could consider other data models. 

In the Health Level Seven International® (HL7®) community, the Clinical Quality Improvement and Clinical Decision Support (CDS) Work Groups harmonized efforts to express eCQM (QDM) and CDS artifacts (virtual medical record). The result is an HL7 Fast Healthcare Interoperability Resources® (FHIR®) Implementation Guide, QI-Core, which includes a detailed mapping of QDM concepts. QI-Core-related tooling allows eCQM developers to use it directly to author eCQMs in FHIR. QI-Core specifically builds directly on each FHIR version to assure consistency of eCQM expressions and the evolving method for data interchange and interoperability. The eCQI Resource Center includes further information about FHIR and transition efforts.

Last Updated: Sep 13, 2023