Clinical Quality Language Engine
An experimental CQL execution engine for analyzing FHIR healthcare data at scale
CQL is a domain specific language designed for querying and executing logic on healthcare data. CQL excels at healthcare data analysis such as defining quality measures, clinical decision support, cohorts or preparing data for dashboards. CQL is designed for healthcare with first class support for terminologies, easy querying of FHIR via FHIRPath, graceful handling of mixed precision or missing data and built in clinical helper functions. You can find an intro to the CQL Language at https://cql.hl7.org.
This repository contains an experimental CQL execution engine in Go, along with various supporting tools and ecosystem connectors. See the Getting Started section to get up and running quickly.
An example CQL snippet.
Features
Notable features of this engine include:
- Built in explainability - for each CQL expression definition we produce a tree that traces through the data and expressions involved in calculating the final result
- Built in custom CQL parser, reducing project dependencies and allowing optimizations between the parser and interpreter
- Benchmarked and optimized to be fast and memory efficient
In addition to the engine this repository has several tools that make it easy to launch and productionize CQL:
- A scalable Beam job for running CQL over large patient populations
- A CLI for easy configuration
- Integration into Google Cloud Storage
Limitations
This CQL Engine is experimental and not an officially supported Google Product. The API to call the engine and the format of the results returned are subject to change. There is limited support of certain parts of the CQL Language:
- Only the FHIR version 4.0.1 data model is supported
- Only the Patient Context is supported
- Not all system operators are supported
- No support for Interval/List Promotion and Demotion
- No support for related context retrieves
- No support for uncertainties
- No support for importing or exporting ELM
- No support for Quantity unit conversion
Getting Started
There are several different ways to use this CQL engine, and get up and running quickly. Click on the links below for details:
- Web Playground: A local interactive web playground in the browser, to quickly experiment with our CQL engine. Includes CQL syntax highlighting and a basic FHIR editor.
- CLI: A command-line interface to run this CQL engine over small populations or for quick experimentation.
- Apache Beam: The Beam pipeline is recommended when running CQL over large patient populations.
- REPL: An interactive command line REPL for quick CQL explorations and experiments.
- Golang Module: The CQL execution engine can be used as a Go library via the CQL golang module. The Retriever interface can be implemented to connect to a custom database or FHIR server. The Terminology Provider interface can be implemented to connect to a custom Terminology server.
⚠️ Warning: When using these tools with protected health information (PHI), please be sure to follow your organization's policies with respect to PHI. ⚠️
Documentation
If you are interested in how this engine was implemented see docs/implementation.md for an overview of the codebase.
Contributors
We would like to recognize those who were significant contributors to the initial squash commit of this project:
Kai Bailey, Suyash Kumar, Evan Gordon, Ryan Brush, Lisa Yin, Other Googlers
These are in order of number of changes. Bolded contributors sent over 100 changes each to the initial commit.
Tech Lead: Suyash Kumar
Product Manager: Chris Grenz
Eng Manager: Ed Nanale
Contributors since the initial squash commit can be seen in the contributors tab.
Thank you to all contributors!