For information regardig the Group File accessory file, see its separate documentation.

The goal of the LOINC Groups project is to create a flexible, extensible, and computable mechanism for rolling up groups of LOINC codes for various purposes. Representative use cases include:

  • Aggregating data for displaying on a flowsheet within an EHR system
  • Retrieving data for quality measure reporting
  • Collecting data for research

This is a work in progress and the contents of the file and the groupings MUST be validated by users prior to implementation in any aspect of clinical care. LOINC Groups have a Beta status. We do not have yet a schedule for promoting Groups to a production status.

Also, LOINC Groups themselves are NOT meant to be targets of mapping. That is, they are designed for use to aggregate existing data identified with LOINC codes. Don’t map your local test codes to LOINC Groups; you’ll be throwing away information.

9.6.1 Example use of Groups

Maybe you’re creating a flowsheet display within an EHR system. Or, maybe you’re retrieving data to fulfill a quality measure report. Perhaps you are processing data from many sources for a research project.

Of course, there’s the generic LOINC concept 29463-7 Body weight. But when you search the LOINC database you find others. What about these?

  • 8341-0 Dry body weight Measured
  • 8338-6 Body weight Measured –ante partum
  • 8345-1 Body weight Measured –post partum
  • 8350-1 Body weight Measured –with clothes
  • 8351-9 Body weight Measured –without clothes

The data inside many EHRs and clinical data warehouses are stored, appropriately so, with these granular LOINC codes that make fine grained distinctions. The problem is that for your purpose, you want to treat them similarly.

As you scan further down the list of terms though, you notice some “special” (a.k.a. oddball) terms that need to be excluded. You definitely need to limit to quantitative terms only, so you don’t get things like 8337-8 Body weight special circumstances, which is used to record things like patient position and other special environmental factors about the measurement.

Even with only quantitative terms, there are other specialized measurements to exclude that aren’t actual patient weights, such as:

  • 73965-6 Body muscle mass/​Body weight Measured
  • 8336-0 Body weight [Percentile] Per age Measured
  • 73964-9 Body muscle mass Calculated

You could write custom lists that enumerated all the possible LOINC codes of interest or keep coming up with more complicated search criteria, but that’s hard to maintain at scale across many tests or measurements you may be interested in. The LOINC Groups project aims to give you a flexible, extensible, and computable mechanism for rolling up Groups of LOINC codes for various purposes.

9.6.2 Accessing LOINC Groups

There are two primary means of obtaining LOINC Groups content for use in your systems.

First are the CSV files included in the LOINC download file available from the Downloads section of our website. You will find the GroupFile directory within AccessoryFiles. See the GroupFile_Readme.txt document for information on individual file structure.

You can also programmatically retrieve Groups as FHIR ValueSets using the LOINC Terminology Service.

If you would like to quickly find Groups, you may do so using our web-based SearchLOINC tool. Simply change the search scope to Groups and enter your query.

9.6.3 Patterns for constructing ParentGroup names

Each ParentGroup is named as a concatenation of the:

  1. High-level group concept;
  2. Axes that are the same for each term in a given group in angle brackets;
  3. If applicable, axis values that are purposely grouped together in a given group in angle brackets; and
  4. Axes that are purposely ignored and therefore automatically grouped together in angle brackets.

For example, the ParentGroup CHEM<SAME:Comp|Prop|Tm><Sys:ANYBldSerPlas><ROLLUP:Meth> contains:

  1. Terms in the CHEM (Chemistry) class;
  2. Where all of the LOINC terms in each individual group have the same Component, Property, and Time;
  3. Where the LOINC terms in a given Group can have a System in ANY of the blood, serum or plasma categories, such as: Bld, BldA, Ser/Plas, etc. (with a few exceptions such as cord blood and dried blood spot); and
  4. Terms are rolled up into a single Group regardless of whether they are methodless or have a specific Method. In other words, ANY Method (including null) is allowed.

9.6.4 Patterns for constructing Group names

Each Group is named as a concatenation of the following pieces delimited by vertical bars (|):

  1. Values in the axes that contain the same value for all LOINC terms in a Group, which corresponds to the first set of angle brackets in the ParentGroup; and
  2. Label assigned to the set of values in a given axis that are purposely grouped together, which corresponds to the second set of angle brackets in the ParentGroup.

Note that the axes that are automatically rolled together, corresponding to the third set of angle brackets in the ParentGroup, are not represented in the individual Group names.

For example, the Glucose|MCnc|Pt|ANYBldSerPlas Group, which is part of the CHEM ParentGroup described on the left, contains terms that have:

  1. Component of Glucose, Property of MCnc, and Timing of Pt;
  2. ANY blood, serum or plasma System (with those noted exceptions); and
  3. ANY Method

9.6.5 Example Group and name

To see how these Group names correspond to the list of LOINC codes they aggregate, let’s take the example of this group:

Glucose|MCnc|Pt|ANYBldSerPlas

  • 2339-0 Glucose [Mass/volume] in Blood
  • 2340-8 Glucose [Mass/volume] in Blood by Automated test strip
  • 2341-6 Glucose [Mass/volume] in Blood by Test strip manual
  • 32016-8 Glucose [Mass/volume] in Capillary blood
  • 41653-7 Glucose [Mass/volume] in Capillary blood by Glucometer
  • 2345-7 Glucose [Mass/volume] in Serum or Plasma
  • 74774-1 Glucose [Mass/volume] in Serum, Plasma or Blood
  • 41651-1 Glucose [Mass/volume] in Arterial blood
  • 41652-9 Glucose [Mass/volume] in Venous blood
  • 6777-7 Deprecated Glucose [Mass/volume] in Serum or Plasma

As you can see from the syntax of the Group name, this collects all LOINC terms that have Component of Glucose, Property of MCnc, and Timing of Pt; ANY blood, serum or plasma System (with those noted exceptions); and ANY Method.