Business Rules For Users Mapping Their Local Panels To Loinc Panels

12.1 Business rules for users mapping their local panels to LOINC panels

Through discussion with the ACLA, the S\&I Framework aLOINC Order Code Initiative, and others, the LOINC Committee has vetted a set of business rules to help LOINC users understand how to compare their panels to a LOINC panel. These rules help clarify what variation is allowed within the LOINC panel definition that still constitutes a “match” for their panel. In these rules, we use “element” to mean a child LOINC that is a member of the panel definition.

12.1.1 Must contain all of the required elements

To establish equivalence (e.g. for mapping), a user panel must contain all of the required elements of a LOINC panel. Some of the other business rules define allowable substitutions, but the general rule is that all required elements must be present in the user panel.

12.1.2 No extra primary measurements

A user panel cannot be considered equivalent to a LOINC panel term if it contains additional primary measured tests that are not part of the LOINC panel definition.

In Fall 2020, the Laboratory LOINC Committee decided that an exception to this rule includes LOINC panels that contain terms that are representative for the type of testing being done but where the specific list of analytes tested may vary across geographic region or laboratory. In this case, it is the reporting laboratory’s responsibility to use the set of LOINC codes that are appropriate for reporting the results for the individual tests performed, even if all of those LOINC codes are not included in the LOINC panel. Examples of such panels include:

• Allergen panels that representing testing for individual components within an allergen category, such as 49222-3 Food allergen panel – Serum and 51662-5 Core respiratory allergens panel – Serum
• Autoimmune serology panels that represent testing for autoantibodies associated with a particular category of autoimmune disorders , such as 94708-5 Encephalopathy autoimmune Ab panel – Cerebral spinal fluid and 94712-7 Movement disorder autoimmune Ab panel – Cerebral spinal fluid
• Multiplex microbiology panels that represent testing for microorganisms associated with infections of a specific body region, such as 88569-9 Ocular pathogens panel – Cornea or Conjunctiva Qualitative by NAA with probe detection and 92695-6 Gastrointestinal bacterial pathogens panel – Stool by NAA with probe detection

12.1.3 Optional elements are optional

A user panel can be considered equivalent to a LOINC panel term whether or not it contains the elements marked as optional in the LOINC panel definition.

12.1.4 Substitutions related to Method

Panel elements that do not contain a Method specification (i.e. the Type of Method part is null) can be treated as a “representative” term that a user could replace with another LOINC term that differed only by specification of Method.

For example, LOINC contains an adenovirus panel:

55160-6 Adenovirus IgG and IgM panel - Serum

with two elements that lack Method specification:

13914-7 Adenovirus IgG Ab [Units/volume] in Serum

5042-7 Adenovirus IgM Ab [Units/volume] in Serum

If a user had a local panel that was similar but had instead mapped to terms that specified the Method of EIA, they may wonder whether their panel was equivalent to the panel in LOINC. Using this business rule, the answer is yes. Either or both of the methodless LOINC panel elements could be replaced by these method-specific LOINC terms that are equivalent on the other attributes:

51822-5 Adenovirus IgG Ab [Units/volume] in Serum by Immunoassay

51823-3 Adenovirus IgM Ab [Units/volume] in Serum by Immunoassay

However, when a panel element measures an analyte by a particular method, then the LOINC term reported for that analyte would have to be done by that method. Neither replacement by a methodless term nor by a different method would be allowed.

12.1.5 Substitutions for mass versus substance Properties

LOINC defines different terms that distinguish between mass-based and substance-based (moles/milliequivalents) measures for a single analyte. Different jurisdictions vary in whether they favor reporting in mass units (e.g. mg/dL) or molar units (e.g. mmol/L) for certain analytes.

In order to promote the international reuse of panels, the LOINC Committee has agreed (at its June 2015 meeting) to allow users to substitute panel elements that a) agree on all other LOINC parts, and b) contain an analogous molar Property to a reference element with a mass Property or vice versa.

To illustrate, panel element terms with the Property of mass concentration (MCnc) could be replaced by substance concentration (SCnc) terms, mass rate (MRat) terms could be replaced by substance rate (SRat), terms etc. For example, in the Lipid panel with direct LDL – Serum or Plasma (LOINC: 57698-3) a user could make substitutions as below and still have a comparable panel:

And so forth.

12.1.6 No substitutions of quantitative/semi-quantitative for qualitative (and vice versa)

A quantitative or semi-quantitative panel element (e.g. one that has a Scale of Qn or SemiQn) cannot be replaced by a qualitative term (e.g. one that has a Scale of Ord) and have the panel be considered equivalent. Likewise, qualitative terms cannot be replaced by quantitative terms in the panel definition.

12.1.7 Panels and reflex (reflexive) testing

LOINC contains a small number of panels specifying the inclusion of reflex (or reflexive) testing. Some of these were created to take the American Medical Association’s reflexive CPT codes into account, and some were for very specific testing algorithms as recommended by professional organizations. In May 2020, the Lab LOINC committee decided that going forward, panel names would not specify reflex testing (i.e., the Component will not contain “W Reflex”), and that existing and future panels that contain the appropriate concepts for the testing being done could serve as reflex panels regardless of the name. We continue to review and update the names and required/optional/conditional elements of existing panels, and we welcome your input regarding panels that need review.

12.1.8 Special case of differential counts (including conventions for not reporting zero counts)

Panels, like blood differential counts and urinalyses, for which zero counts (e.g. for the % of blast cells) are usually not reported explicitly present a special case. These are included in the panel definition but are marked as conditional (C) to signal that under some circumstances (e.g., when they have a value of zero), they are not reported. Differential counts present another problem in that a given cell type could be reported as a fraction of the total WBC and/or as an absolute count, so both species are included in the panel for differential counts, but as discussed above, both are not required in the report.

12.1.9 Panels with only narrative definitions of the elements they should contain

As described above, in certain special cases, such as public health and veterinary testing, LOINC may define a panel term by a narrative definition rather than enumerating the set of child elements. In such cases, the user must read the definition and use their professional judgment as to whether or not their local panel is comparable to the LOINC panel.

12.1.10 Substitutions related to System

Panel elements with a general System may be replaced with other LOINC terms that only differ by having a more specific System. For example, terms with a System of Respiratory.upper may be replaced with LOINC terms with a System of Nph (nasopharynx), Throat, or Nose, and terms with a System of Genital may be replaced with LOINC terms with a System of Vag (vaginal), Cvx (cervix), Urethra, etc. Substitutions with terms that have less specific Systems are NOT allowed; for example, you may not substitute a term with System of Respiratory for a Sputum term.

Substitutions with terms with unrelated Systems are also NOT allowed, such as substituting a LOINC term with System CSF for a term with System Ser/Plas, or substituting a term with System Urine for a term with System Respiratory.

The following table illustrates acceptable substitutions related to System.

12.1.11 Single primary results

If a single primary result (either measured or derived) is being reported along with secondary results that serve as supportive or interpretive findings, the LOINC code for the primary result should be used as the order code. For example, if the ratio of an analyte to creatinine is the primary result but is report along with the creatinine result, the LOINC term for the ratio should be used as the order and a LOINC panel will not be created. This recommendation was agreed upon by the Laboratory LOINC Committee in March 2021.