LOINC – IVD Test Code (LIVD) Mapping
1.0.0 - STU 1

LOINC – IVD Test Code (LIVD) Mapping, published by HL7 International / Orders and Observations. This guide is not an authorized publication; it is the continuous build for version 1.0.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/livd/ and changes regularly. See the Directory of published versions

## Glossary

Page standards status: Informative

Analyte: CLIA defines an analyte as “a substance or constituent for which the laboratory conducts testing.”[1] Lab Tests Online indicates in lay terms, it may be called a test[2].

Some laboratories and IVD vendors may use the term parameter instead of analyte. Others may use assay to describe the test process. Synonyms: parameter, assay, result.

Assay: According to LabTestsOnline.org, an assay is a” procedure used to detect or measure a substance or reaction.” It is also may be known as a test.[3]

CLIA: CLIA is the abbreviation for the Clinical Laboratory Improvement Amendments of 1988, which is federal law regulating laboratory testing in the United States.”

In Vitro Diagnostics (IVD): Instruments and software systems which utilize assays for the analysis of patient specimens outside the body.

Test Order: Although this term is frequently used to indicate what the physician is requesting of the laboratory to be performed on a patient specimen, for LIVD, it is referring to the term built in the LIS corresponding to what the performing laboratory performs when requested by the provider. The name in the LIS build for the test order is what is contained in the laboratory’s Specimen Collection Manual (required by CLIA) or laboratory compendium or order catalog and provided to all locations where test ordering occurs. The name of the test order established by the performing laboratory may be the same or different than the name for the test order (for the same test) as displayed in CPOE EHR systems or other LISs who request the test order.

The test order may be for a single test requested and resulted such as a potassium level. It may also be a panel order consisting of multiple test results such as a complete blood count (CBC) which includes results for hemoglobin, hematocrit, white cell count, etc. Test orders may be grouped together in convenience panels for physicians to order multiple tests (panels or single tests) in a single action such as a click.

Test Result: The test result corresponds to the analyses performed by a laboratory in response to an order. The test result is the name built in the LIS and reported on the test report of record and is the official naming convention by the performing laboratory. This name may or may not be the same as the analyte or assay utilized in performing the test analysis.

For example, an IVD vendor offers a serum glucose assay. The laboratory performs the assay on a patient specimen to obtain a glucose result value, which travels across the instrument interface or is manually entered by a laboratory professional into the LIS. The LIS has multiple glucose test results that are built and used for reporting serum glucoses. One of these is “glucose level,” which would correspond to the IVD vendor provided LOINC code. However, another LIS test result is “1 hour glucose tolerance test level.” This test result would require another LOINC code corresponding to different details for the test result reported. A different LOINC would need to be mapped to it, which reflects these test result differences. Both test results would produce numeric test result values in this example.

LOINC codes pertaining to the test result information are provided in the LIVD standard, which can be used in many cases to map to the test result(s) built in the LIS. In other cases, such as for most challenge and timed tests, the LOINC may correspond to the assay and analyte, but not the LIS test result. The laboratory professional can use the IVD provided LOINC as a guide to assist them in looking up the appropriate LOINC for their test result for use in the LIS and other downstream mappings.

Test Result Value: The Test Result value is what has been determined via analysis of a patient specimen and associated with a specific test result. It can be numeric as reported for many IVD assays and associated with units and a reference range. In other cases, it may be qualitative with a value, such as detected or not detected per the manufacturer’s package insert instructions. In other cases, the value may be a short answer or phrase such as the name of an organism reported. In more manual testing processes and interpretations, longer sentences or narratives may be reported as a test result value.

Test result value mappings will vary depending on the context and regulatory requirements for that data for which code systems are required for the mapping(s). For example, numeric test result values are unable to be codified. Qualitative test result values are required to be mapped to SNOMED CT Codes from the Qualifier Values hierarchy in the US. In addition to the SNOMED CT codes, some implementers may wish to map LOINC Answer codes to qualitative test result values. If the qualitative test result value is an organism, then the SNOMED CT codes from the Organism hierarchy are the required mapping in the US.

Test System: CLIA defines a test system as “the instructions and all of the instrumentation, equipment, reagents, and supplies needed to perform an assay or examination and generate test results.” [1]

Glossary Term examples:

Test Order (LIS build) | Order LOINC (out of scope) (LIS) | Order LOINC Long Name (LIS) | IVD Analyte (requested by order) | IVD Result LOINC Code (LIVD) | IVD Result LOINC Long Name (LIVD) | IVD Result Value | Units | Test Result (LIS build) | Test Result LOINC code (LIS) | Test Result LOINC Long Name (LIS) | Test Result Value (LIS)
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Lytes | 24326-1 | Electrolytes 1998 panel – Serum or Plasma | Sodium (NA) | 2951-2 | Sodium [Moles/volume] in Serum or Plasma | 138 | mmol/L | Sodium Ser | 2951-2 | Sodium [Moles/volume] in Serum or Plasma | 138
Lytes | 24326-1 | Electrolytes 1998 panel – Serum or Plasma | Potassium (K) | 2823-3 | Potassium [Moles/volume] in Serum or Plasma | 3.9 | mmol/L | K Ser | 2823-3 | Potassium [Moles/volume] in Serum or Plasma | 3.9
Lytes | 24326-1 | Electrolytes 1998 panel – Serum or Plasma | Chloride (Cl) | 2075-0 | Chloride [Moles/volume] in Serum or Plasma | 102 | mmol/L | Chloride Ser | 2075-0 | Chloride [Moles/volume] in Serum or Plasma | 103
Lytes | 24326-1 | Electrolytes 1998 panel – Serum or Plasma | CO2 | 1963-8 | Bicarbonate [Moles/volume] in Serum or Plasma | 28 | mmol/L | CO2 Ser | 1963-8 | Bicarbonate [Moles/volume] in Serum or Plasma | 28
2 hour Urine Potassium | 57379-0 | Potassium [Moles/volume] in 2 hour Urine | Potassium (K) | 2828-2 m | Potassium [Moles/volume] in Urine |  | mmol/L | 2h U K | 57379-0 | Potassium [Moles/volume] in 2 hour Urine |
3 H GTT (Glucose Tolerance Test) | 50608-9 | Glucose tolerance 3 hours gestational panel – Serum or Plasma | Glucose | 2345-7 | Glucose [Mass/volume] in Serum or Plasma | 99 | mg/dL | Fasting Gluc | 1558-6 | Fasting glucose [Mass/volume] in Serum or Plasma | 99
3 H GTT (Glucose Tolerance Test) | 50608-9 | Glucose tolerance 3 hours gestational panel – Serum or Plasma | Glucose | 2345-7 | Glucose [Mass/volume] in Serum or Plasma | 150 | mg/dL | 1H Gluc | 20438-8 | Glucose [Mass/volume] in Serum or Plasma- 1 hour post dose glucose | 150
3 H GTT (Glucose Tolerance Test) | 50608-9 | Glucose tolerance 3 hours gestational panel – Serum or Plasma | Glucose | 2345-7 | Glucose [Mass/volume] in Serum or Plasma | 250 | mg/dL | 2H Gluc | 20436-2 | Glucose [Mass/volume] in Serum or Plasma- 2 hours post dose glucose | 250
3 H GTT (Glucose Tolerance Test) | 50608-9 | Glucose tolerance 3 hours gestational panel – Serum or Plasma | Glucose | 2345-7 | Glucose [Mass/volume] in Serum or Plasma | 200 | mg/dL | 3H Gluc | 20437-0 | Glucose [Mass/volume] in Serum or Plasma- 3 hours post dose glucose | 200

[1] CLIA regulations https://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=9b42cf158b7c913fe20af21d8d820148&ty=HTML&h=L&mc=true&n=pt42.5.493&r=PART

[2] Lab Tests Online Analyte Definition https://labtestsonline.org/glossary/analyte

[3] Lab Tests Online Assay Definition https://labtestsonline.org/glossary/assay