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Parenthesis, Brackets and Braces in LOINC®


Parentheses, brackets and braces – called “enclosing glyphs” – are used in LOINC® for different purposes. Understanding their usage helps you differentiate them and select the correct term for your requirements.

The most used of the glyphs is the parentheses, also called “round brackets or round braces”. They are used for mainly 4 purposes:

1. Control the order of operations in an expression
2. Supply parameters to a method,
3. Provide the short name/abbreviation of a substance
4. Act as a grouper (allowing you to apply a quantifier to the entire group or restrict the group to specific limits)

Here are some examples in LOINC®:

LOINC#   Component  Property Timing   System  Scale
 15223-1  (Artemisia dracunculus+Levisticum officinale+Origanum majorana) Ab.IgE  PrThr  Pt  Ser  Ord
 53233-3  Carnitine.free (C0)/Palmitoylcarnitine (C16)  SRto  Pt  Bld.dot  Qn
 39370-2  (Views) + (view^W manual stress)*  Find  Pt  Lower extremity.right  XR

*In this radiology example, the parentheses are used to indicate which view types the maneuver is related to (this will include an X ray of the right ankle with multiple views plus another view with manual stress on the ankle).

Brackets (also known as Square Braces) are used in LOINC® mainly to indicate special, non-metric units of measurement (to learn more, please read the Tip of the Month on “Working with UCUM ”). In the example below, the [ft_i] refers to the unit of measurement “international foot”. Brackets can also be used to show the chemical structure of a substance, such as in the example below for LOINC 78360-5.

LOINC#  Component  Property   Timing  System Scale   Method
 83163-6  Number of 10 [ft_i] marks^2M post trial start  Num  Pt  ^Patient  Qn  
 78360-5  Acyl CoA dehydrogenases  CCnt  Pt  Fibroblasts  Qn  [9,10-3H] myristate substrate


The curly braces, often called just “braces”, curly brackets, or squiggly brackets, are also used in UCUM. They contain annotations that are traditionally used in clinical laboratories. Any annotation within curly braces can be excluded and the LOINC® term will not lose its meaning. In the examples below, U/g{Hb} stands for “units per gram hemoglobin”. To computers, it’s meaningless when parsed, but they are familiar and quite helpful to lab personnel. In the Component, System and Method field, the curly braces act to narrow a set of possible values. Look below at LOINC 33992-9. The “Primary pain location” is narrowing the set of possible values to anatomic regions where pain is felt or most intense.

LOINC#   Component  Property Timing  System  Scale  Method  Example UCUM Units 
 49230-6  Acetylcholinesterase  CCnt  Pt  RBC  Qn    U/g{Hb}
 33992-9  Pain trigger point  Anat  Pt  {Primary pain location}  Nom    

When you are searching in the LOINC® RELMA tool and would like to see all the LOINC terms that use one of the enclosing glyphs, such as parentheses, you can type the string “Punctuation : Parenthesis” in the search box, as follows, and all terms containing parentheses will be shown:

For LOINC terms that contain brackets, you would use:
Punctuation : Bracket

And for LOINC terms that contain curly braces, you would use:
Punctuation : Brace

We hope this is an interesting LOINC® hack for you.
If you have other terminology hacks that you’d like to share or need help with terminology mapping , please contact us.