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Understanding LOINC® Groups

The LOINC® groups project by the Regenstrief Institute aims to give you a flexible, extensible, and computable mechanism
for LabTestsTubes400rolling up groups of LOINC codes for various purposes.
Starting in 2017 with support by the National Center for Advancing Translational Sciences, LOINC groups organize collections of codes as defined by LOINC’s six-axis terminology model.
For example, rather than searching for individual variations of ‘blood glucose measurements’, LOINC groups can bundle blood glucose measurement codes under a single source.

LOINC groups are structured by their defined axis values. This is done by creating high-level Parent Groups which are used as templates for sub-groups and the codes contained within each sub-group.
Let’s look at the structure of a LOINC Parent Group as an example: 

 LOINC Parent Group
Parent Group Name  CHEM<SAME: Comp | Prop | Tm> <Sys:ANYBldSerPlas> <ROLLUP: Meth> 
 LOINC® Axis  LOINC Axis Requirements
CHEM  LOINC codes must be in the Chemistry class
SAME: Comp | Prop | Tm  LOINC codes must have the same Component, Property, and Time axis
Sys: ANYBldSerPlas  LOINC codes can have a System of any blood, serum, or plasma categories
ROLLUP: Meth  LOINC codes are rolled up into a single group regardless of whether they are methodless or have a specific method


Parent Groups contain broad ranges of codes due to fewer axis constraints. Sub-groups are more granular, further specifying axis value requirements for codes under the Parent Group template. This allows sub-groups to constrain codes according to a specific use case. To see how Parent Groups correspond to a list of sub-group LOINC codes, we need to create a sub-group that constrains the list of aggregated Parent Group codes. Let’s take a look at LOINC group LG7967-5 Glucose|MCnc|PT|ANYBldSerPl as an example:

LOINC Sub-Group 
Sub-Group Name  Glucose | MCnc | Pt | ANYBldSerPlas 
 LOINC® Axis  LOINC® Axis Requirements
Component  LOINC codes must have a Component of Glucose
Property  LOINC codes must have a Property of Mass Concentration (MCnc)
Time  LOINC codes must have a Time of Point in Time (Pt)
System  LOINC codes can have a System of any blood, serum, or plasma
Method  LOINC codes can have any Method or remain methodless


By specifying the required sub-group axis values, the list of codes should contain ‘like’ terms with similar definitional meaning or use. The following list is an example of the codes contained within LOINC sub-group LG7967-5 Glucose|MCnc|PT|ANYBldSerPl.

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
41651-1  Glucose [Mass/volume] in Arterial blood
41652-9  Glucose [Mass/volume] in Venous blood


As more use cases are identified, LOINC groups aim to enable users with understandable, reproducible, and useful collections of codes that better group similar content. Currently, the Regenstrief Institute is asking the community to assemble and submit LOINC groups through the LOINC Groups Submissions page. Submitted groups will be reviewed by the community and potentially nominated for inclusion in future LOINC® releases.