Monday, July 23, 2012

What is HQMF?

John Moehrke asked for this one.  I've written nearly a double dozen posts on HQMF, and more than three dozen on Query Health, but never stopped to explain what HQMF is.

The Health Quality Measure Format (HQMF for short), is an HL7 standard format for documenting the content and structure of a quality measure.  It is intended to represent quality measures used in a healthcare setting.  It is an XML document format based on the HL7 Reference Information Model (RIM), just like CDA is, but instead of describing what happens in a patient encounter, the HQMF standard describes how to compute a quality measure.

There are six or eight key components of a quality measure (depending upon measure type and level of detail).  These are structured at three different levels of detail.  At the first level of detail is metadata describing the quality measure.  This goes into the header of the document, and describes the who wrote it, the dates over which it is valid, who validated it, and other details about how the measure works or is used.  The metadata makes it easy to find the quality measure.  You can write a valid HQMF document and only include this level of detail.  The body of the document can be written in a PDF or any other multimedia format.  This level of detail is intended to support legacy documentation on quality measures.

The second level of detail provides a human narrative description of the quality measure in three (or four) sections:
  1. Measure Description
  2. Data Criteria
  3. Measure Population
  4. Measure Observations
The measure description simply contains human readable narrative describing the measure, it's purpose, how it works, et cetera.  The data criteria section describes the "data of interest" to the measure.  This is where you find descriptions of the events, statuses and attributes of those events that need to be captured to make the measure effective.  The measure population section describes the major components of the measure, including the initial population, the numerator, the denominator, and various special cases (known as exclusions or exceptions depending upon how they are treated).

A typical ratio measure has criteria describing the initial population, and criteria for numerator and denominator.  These criteria explain how to counts of patients (or other items) that match the specified criteria.

Other measures (e.g., a continuous variable measure), need to describe not just what to count, but how to compute from the items selected in the initial population (e.g., to compute average ED wait times).  How those  observations are computed is described in the measure observations section.

The third level of detail needed to automate measure computation is provided in machine readable entries in the last three sections.  These entries appear when the measure is specified at the highest level of detail.   These entries provide  the computer with instructions on how to count and compute the results of the measure.  For ratio measures, these entries describe how to combine the data of interest using Boolean logic to select the items to count.  For measure observations, these entries describe what items need to be computed with, and the measure observation definitions then describe the computation.

HQMF Release 1.0 was developed and balloted in 2009 by HL7 as a Draft Standard for Trial Use (DSTU), and was published in March 2010 as a DSTU (and has now expired).  During the two year DSTU period, the standard was used by NQF to retool more than 100 existing quality measures into electronic format.  NQF also developed the Measure Authoring Tool to create HQMF documents.  The ONC S&I Framework adopted and adapted the standard for use in its Query Health project, designed to allow health data to be queried by external sources.  (See my series of posts on Query Health).

The Query Health adapted version of HQMF became the foundation of Release 2.0 of the HQMF standard, currently being balloted by HL7.  This will also become a Draft Standard for Trial Use for two years.  MITRE has developed an experimental transform that converts HQMF R1 to HQMF R2 format, with some limitations.  I've heard reports that they've been able to use it successfully on about 80% of the NQF retooled measures.

HQMF can do more than just define "how to count".  The HQMF standard can be used to describe what the output of counting should look like.  When used in combination with the QRDA specification (an implementation guide on the HL7 CDA), HQMF can tell you what data needs to go into the QRDA.  It's also possible to use an HQMF document with just a data criteria section to describe what needs to be sent over an interface, or to describe the entries that should be present in a CCDA document (a variation on the use already designed into HQMF and QRDA).  So HQMF is the "query", and QRDA is (or can be) the output of that query.  There are three different categories of QRDA.  As related to HQMF, QRDA Category I is patient level data for a single patient.  A collection of QRDA Category I documents can be used as the data inputs to a measure calculation.  QRDA Category II can be used to report on the patient data actually used to calculate the measure, enumerating all patients and their data in a single document.  Finally, QRDA Category III can be used to report the aggregated results.  QRDA Category I is fully described in the HL7 QRDA DSTU.  Category II and Category III are alluded to, but not described in detail.  It's easy to figure out that QRDA Category II would be very similar to Category I, but just contain more patient data.  The format for QRDA Category III is currently being worked on (in fact, I missed a meeting today because I'm teaching about HQMF and QRDA).

Given current developments and implementation efforts that have been going on in Query Health and for retooled measures, I expect HQMF to be on the short list of standards to be considered for Meaningful Use Stage 3.

This post was updated on Tuesday, July 24th, to address comments below. I clarified what HQMF is, added more information about the third level of detail, and described a bit more about QRDA.


  1. Thanks. This is helpful.

    So this is an XML file? Derived from the HL7 RIM?

    To be clear, this is a file that explains to a healthcare provider organization what the requesting organization wants to know. So it is a Query format, not a Results format.

    What is the results format? Clearly this is not a CDA document, as the results are not patient specific. Right?

    1. Yes, this is an XML file derived from the HL7 RIM. It explains what the requesting organization wants to know. The results format can be an HL7 QRDA Category III document. Clearly this shouldn't be a CDA Release 2.0 document, as the results are not patient specific, but people are being flexible on that point given the need for it, and the challenges in creating a whole new V3 standard when CDA is So close. Even so, my hope is that the CDA R3 model avoids the necessity of making that distinction in the overall standard.

      There are outputs that would be patient specific, such as the QRDA Category I, which CMS expects for PRQS reporting.

  2. Thanks for this summary, it is very helpful. I have a couple of comments:

    1. When you say that Measure Population describes the initial population, does that mean the entire initial population data is provided in this section? That would be the most complete description of the initial population and could then be used to compute the result again if someone needed to check the result. Is the initial population data available otherwise for checking of the result?

    2. You never described "Measure Observations". Also you said there were three levels of detail, but you only clarify the components that make up the first two and you never mention the third level of detail. I assume the last level of detail are the last three sections that you mention, but you don't make that clear.

  3. The measure population section describes what patients (or encounters or other items being counted) are enumerated, but does not enumerate them explicitly. That enumerated list of patients and data could be an output using a QRDA Category II document.

    I'll update the post with the missing level of detail. It is covered, but perhaps not as well as you'd like.

  4. Thanks for the clarifications Keith. In the third section, is there a standard language used to describe the algorithm? Or is a header for the section used to indicate what language is used?