This section last updated: 2023-08-15 (4 months ago)
The following sections describe in more detail the search constraints you may employ to narrow searches performed against the LOINC database. The goal of the RELMA program is to aid users in finding the smallest pool of candidate LOINCs possible for each local term so that users can quickly and efficiently map their local terms to LOINC. Each restriction is intended to narrow results based on various facets of the LOINC data set.
The options in this group are unique in that they use information about the current local code in conjunction with attributes of the LOINC term to eliminate incompatible LOINC terms from the search results. All of the other search restrictions are based on attributes of the LOINC code itself. This feature makes these option especially valuable when used on the mapping screen with your own local codes.
Exclude terms inconsistent with local units
When this option is checked, a search will only return LOINC codes that have a PROPERTY attribute compatible with the units provided on the search on mapping screen. This option is checked by default and is automatically checked when you click the "Reset Limits" button in the "Mapping" tab.
Consider the search for PROTEIN UA provided in the SAMPLE local term file. The figure below shows a search without the Units Restriction enforced (you can tell that the Units Restriction is turned off because the word "Units" appears gray in the status bar at the bottom of the screen). The search returned more than 300 candidate LOINCs (displayed in the results grid). This is quite a few terms to examine by hand to determine which one most closely matches the local term "UTP4R".
By enabling the Units Restriction, only LOINC terms with a property of MRat (mass rate) remain. The other candidate LOINCs were eliminated because their properties were not compatible with the term's units of "MG/24 HR". The figure below shows that the number of candidate LOINCs dropped significantly and is much more manageable for a user to manually review in order to determine the appropriate map.
Exclude terms inconsistent with specimen
When this option is checked, a search will only return results whose LOINC System is assigned to the local term's lab section. For more information on lab section defaults, see the LAB section of the manual.
Consider the search for OPIATES provided in the sample local term file. The figure below shows a search without the specimen restriction enforced, which returned more than 50 candidate LOINCs (displayed in the results grid).
By enabling the specimen restriction, only LOINC terms with a specimen (a.k.a. System) of UR (urine) remain. The LOINCs removed as candidates from the search were eliminated on UR because the term is a member of the DRUG SCREEN lab section which has only the UR system associated with it. Lab sections can be edited and the user can create custom lab section definitions. Please see the Lab Sections portion of this manual for more information. The figure below shows that the number of candidate LOINCs dropped significantly when the specimen restriction was turned on.
The options in this group control the base set of LOINC codes that are considered when performing a search. There is a check box for each of the four possible STATUS values that a LOINC may have. In general, you will almost always want to map your local codes to LOINC terms that have a status of Active so this check box should almost always be checked. The LOINC manual gives detailed guidance on the use of LOINC terms with a status other than Active.
The other options allow you to include terms with a status of Trial, Discouraged, and Deprecated in your search results. These options can be a handy way to look up older LOINC codes or codes to which you may have mapped your local terms that are no longer appearing in the search results grid. An example of a search that includes deprecated LOINCs is displayed in the figure below. Deprecated terms appear in a strikethrough font and have a "do not" sign to the left of the row number. Discouraged terms appear in the regular font (not strikethrough) but have an American "yield" sign to the left of the row number, and trial terms have an American "under construction" sign to the left of the row number. These variations in the display allow users to easily distinguish between active, trial, discouraged, and deprecated terms in the grid.
The options in this group can be used to further filter search results by eliminating LOINC codes with specific attributes or classifications.
Exclude terms not in the common orders subset
When this option is checked, then the search results will only contain LOINC codes that are present in the Top 300 Lab Order Codes value set ("Value set of universal laboratory order codes from LOINC"), which is described in detail at http://loinc.org/usage.
For example, suppose the user searches for LOINC terms containing the keyword GLUCOSE. If the search restriction is not enforced then the results will include a large number of terms, similar to those shown in the figure below.
If the user enforces the search restriction, then the results set will be much smaller, similar to those shown in the figure below.
Exclude terms with System left or right
When this option is checked, the search will return only results that do not contain the keywords left or right in the System (a.k.a. specimen). The remaining LOINC terms will either be explicitly marked as bilateral or will have no explicit laterality.
For example, suppose your local term file contains a term for ATRIUM. A search on this keyword yields a fairly large number of results as shown in the figure below.
However, if you enable "Exclude terms with system 'left' or 'right'", then the search will yield only a handful of results as the terms with left or right in the system are excluded.
Exclude internal lab use terms
When this option is checked the search will eliminate LOINC terms that are primarily used for internal lab reporting.
Exclude limited use lab orders
When this option is checked the search will eliminate LOINC terms that were created ONLY for indistinct lab ordering (in response to a specific submitter). These terms include dashes in some LOINC fields (e.g. Property, Scale) to indicate that the ordering provider does not care about these attributes. The lab uses the reporting process they have set up for the observation result.
Exclude public health terms
When this option is checked the search will eliminate LOINC terms that are designated primarily for use in the world of public health.
Exclude veterinary terms
When this option is checked the search will eliminate LOINC terms that are primarily used in the field of veterinary medicine.
Exclude honorary terms
When this option is checked the search will eliminate LOINC terms that have been created to celebrate the contributions of an individual.
Exclude non-routine challenge terms
When this option is checked the search will eliminate all challenge tests that are not in the CHAL.ROUTINE LOINC class from the search results.
Exclude method specific terms
When this option is checked, then the search results will only contain LOINC terms that do not contain a method.
For example, suppose the user searches for LOINC terms containing the keywords VIRAL and HEMORRHAGIC. If the search restriction is not enforced then the results will include terms with various Methods as well as those that do not have a Method value, as shown in the screenshot below.
If the user performs the same search and enforces the "Exclude method specific terms" search restriction then only the few LOINC terms that do not contain a method are returned, as shown in the figure below.
Let's take a closer look at the methodless and method-specific LOINC terms that were returned in our original search. If we separate these terms into groups with the same Component, Property, Time, System, and Scale then the following 5 groups are created.
When the "Exclude method specific terms" search restriction was applied, none of the terms in the first group or the last group were returned because all of the terms in these groups are method specific. However, in some cases the user may want to view these terms along with the terms that do not contain a method. This can be accomplished by also checking the "Return method specific terms when no methodless term exists" checkbox. Below are the results when both of the search restrictions are enforced.
From the LOINC FAQ section "Mapping Local Codes to LOINC Questions"
When do I use a methodless code?
As a general rule, the methodless LOINC code is meant to include the LOINC codes with methods. In the hierarchy tree, the methodless terms pertain to methods that are unknown or multiple methods using the same reportable detail. Use a method specific LOINC code when the method has a meaningful clinical difference in the results. Refer to Type of Method (6th Part) of the LOINC Users' Guide for more information.
Many laboratory LOINCs can be classified as either Orders or Observations, while some can be considered as both Orders and Observations. By selecting one or more values from the Order/Obs checkbox group shown in the Search Constraints Screen, the user can choose to favor a specific kind of LOINC (e.g. the user can restrict by orders, observations, both and/or subset). The search restriction corresponds to the ORDER_OBS field in the LOINC table, which is described in the LOINC Users' Guide. By default, "Include Orders", "Include Observations" and "Include Both" is selected. Changes applied to these selections will be persisted by user.
The value "Include "Observation" Terms" tells the program to return LOINC terms where the ORDER_OBS field equals "observation". The figure below shows a search on the keyword "SODIUM" with the ORDER_OBS restriction set to "Include "Observations" terms".
Certain LOINC terms are identical in all respects except for their Property values. In many of these cases, the property only varies based on substance (commonly used in European, Canadian and Australian labs) versus mass (commonly used in American labs). Using the "Favor Property" drop-down box on the Search Constraints Screen, the user can tell the RELMA program that he or she prefers one type of Property over the other (e.g. the user prefers searches to return mass concentrations rather than substance concentrations).
Consider the search for BISMUTH in the figure below, which yields more than 20 candidate LOINCs. Given that our lab measures results in ug per L, our lab would prefer mass concentration LOINCs over substance concentration LOINCs.
By setting the "Favor Property" setting to "Favor Mass", the substance concentration results are eliminated and only the mass concentration results are returned. Leaving this setting selected while the user maps further terms in the local term file will hide future substance concentration tests when there is an equivalent mass concentration test available.
NOTE - Setting this restriction only eliminates LOINC terms where both a mass and a substance version of the term exists. If only a single version of the term exists, it will be returned by the search even though it may not have the correct property type.
Taken from the LOINC Users' Guide:
The pharmaceutical industry has the need for laboratory terms that are not specific as to whether the test measures a substance (substance concentration or substance rate) or mass (mass concentration or mass rate). We have created terms with the properties of MSCNC or MSRAT to represent these more general test observations.
By default, RELMA does not include these terms in search result sets. In order for these terms to be included in searches, the user must set the Pharma MS* search restriction to either "Include MS* Terms" or "MS* Terms Only". The former value will tell RELMA to return both Pharma and non-Pharma terms while the latter value will tell the program to return only Pharma terms. The following examples demonstrate how the value of the Pharma MS* restriction will affect search results.
Consider a search for GLUCOSE SER PLAS. A search that uses the "Include MS* Terms" options returns two extra terms compared to a search that uses the default value for the Pharma MS* restriction (Exclude MS* Terms). The figure below shows those two extra terms in isolation by doing the same search, only this time using a value of "MS* Terms Only" for the Pharma MS* restriction.
The subset Restriction is added to the status bar on the search screen. The search limits the list to set of LOINC codes user has created.
Sample search criteria with subset restriction
Sample search criteria without subset restriction
LOINC hierarchies are available for viewing and searching at https://loinc.org/tree/