This page is part of the Loinc/IVD Mapping FHIR IG (v1.0.0-ballot: STU1 Ballot 1) based on FHIR (HL7® FHIR® Standard) R4. . For a full list of available versions, see the Directory of published versions

LOINC Mapping Summary

When communicating results from a device to the Laboratory Information System (LIS), the following concepts must be mapped:

• The IVD Test (In-Vitro Diagnostic Test) representing the analyte to the LIS Test Result Code; and
• The IVD Result Value to the LIS Test Result's Result Value

Neither the IVD Test, the LIS Test Result, nor the respective IVD Result Values are likely based on industry standard vocabulary. The manufacturer assigns analyte information such as vendor analyte code (transmission code or identifier), a name, and reference identifier, plus associated IVD Result Value codes, while the Laboratory creates LIS Test Results and its LIS Result Values for the tests they provide. Through LIS configuration tools, the IVD Test’s Vendor Analyte Code is associated with one or more LIS Test Result Codes based on context, e.g., IVD Test used with one vs. another specimen would yield a different LIS Test Results. This process has been in place for decades and has been optimized to support the Laboratory’s specific reporting requirements (including conformance to Clinical Laboratory Improvement Amendments (CLIA) for the US).

To enable analytics and clinical decision support, harmonization to a common vocabulary is critical. For laboratory test results, Logical Observation Identifiers Names and Codes (LOINC^(R)) is the coding system of choice, while for non-quantitative, encoded result values, SNOMED and LOINC are both in use to enable a consistent expression. This introducing the question on how to map the LIS Test Result Code to LOINC, as well as corresponding Result Value Code to either LOINC or SNOMED, and do so consistently across all laboratories to enable analytics and clinical decision support reliably.

For various reasons, including but not limited to an LIS communicating the ordered tests to the device using LOINC, the device cannot provide the appropriate LOINC code with the test result. The LIS must provide the mapping as they associate the IVD Test and its IVD Result Value with the LIS Test Result and its LIS Result value respectively. To date this mapping process has relied on a combination of the LOINC registry, RELMA, and the individual’s knowledge of LOINC plus the LIS’ test compendium and further information on the Vendr Analyte Code’s Result Value Codes to arrive at the appropriate LOINC or SNOMED codes for the actual value where applicable.

The device manufacturer can aid in the process by providing a list of suggested LOINC codes for each of their IVD Tests, including context of the result, specimen, and other considerations that would influence the choice, as well as the appropriate LOINC or SNOMED codes for their IVD Result Values. Such guidance would help reduce the scope of potential LOINC and SNOMED codes to consider, thus improving efficiency and quality of the mapping process, particularly across laboratories, i.e., arriving at the same LOINC or SNOMED code for the same test.

The following diagram may help further clarify that:

Note: The IVD Result Value to LOINC answer codes and SNOMED codes to support LIS Result Values to the codes are of of scope for this version, therefore greyed-out.

• The LIS maintains a map between the IVD Test's vendor analyte code and their LIS Test Result code.
• One IVD Test can yield different LIS Test Results depending on specimen and other parameters.
• Each of the LIS Test Results must have a LOINC code associated with it so the results report includes the appropriate LOINC code as well for downstream use.
• Laboratory staff today rely on LOINC definitions (using RELMA or the web based tool), their local mappings, and their expertise/knowledge about the device, test, and parameters, to associate a specific LOINC code to the LIS Test Result Code.
• The LIS also maintains a map between the Vendor Analyte Code's Result Value Codes and the LIS Test Result Code's Result Value Code.
• One IVD Result Value yields one LOINC code or SNOMED code.
• While it may have a map to both, local reporting requirements would yield an LIS to only use the LOINC or only then SNOMED codes.
• Adding the LIVD suggested mappings, where available, enhances the Laboratory staff's ability to arrive more quickly and correctly at the right LOINC and SNOMED codes.

When the laboratory professional builds the test results that their LIS will manage and interact with the devices, they can use the device vendor’s suggestions to more accurately, consistently, and efficiently map the results in their LIS to a LOINC code in context of the device’s IVD Test. Note that, as these are device vendor’s suggestions, the expectation is that the suggested mappings are displayed and assist the laboratory staff to narrow the likely options that fit the laboratory’s intended use based. Therefore, the mappings are not suitable for automated configuration. The following example clarifies the information a laboratory professional would use during their configuration.

Example#1 – Glucose

Vendor Analyte Code = 1067 (Gluc) is mapped in the LIS to:

• LIS Test Result Info = 123 - Glucose CSF mg/dL
• LIS Test Result Info = 456 - Fasting Glucose Urine mg/dL
• LIS Test Result Info = 789 - 1 Hour Glucose Plasma mg/dL

LIVD Mapping Vendor Analyte Code = 1067 (Gluc) suggests:

• Based on vendor comment [comment], vendor result description [result] A, vendor specimen description [specimen] "cerebrospinal", unit of measure "mg/dL", LOINC axes => 2342-4 Glucose [Mass/volume] in Cerebral spinal fluid
• Based on vendor comment [comment], vendor result description [result] B, vendor specimen description "urine", unit of measure "mg/dL", LOINC axes => 63382-6
• Based on vendor comment [comment], vendor result description [result] C, vendor specimen description "serum/plasma", unit of measure "mg/dL", LOINC axes => 20438-8

Consequently, most appropriate mapping:

• LIS Test Result Code = 123 - Glucose CSF mg/dL MAP TO LOINC Code = 2342-4 Glucose [Mass/volume] in Cerebral spinal fluid
• LIS Test Result Code = 456 - Fasting Glucose Urine mg/dL MAP TO LOINC Code = 63382-6 Fasting glucose [Mass/volume] in Urine
• LIS Test Result Code = 789 - 1 Hour Glucose Plasma mg/dL MAP TO LOINC Code = 20438-8 Glucose [Mass/volume] in Serum or Plasma --1 hour post dose glucose

Example#2 - Total Protein (CSF/Urine)

This IVD “test kit” is usually named Total Protein (CSF/Urine) and utilized for the analysis of CSF, Random/Spot Urine, or Timed urine (24 hr, 2 hr, etc) specimens. It is often used to perform body fluid Total Proteins. However, a different IVD “test kit” is typically used for serum/plasma Total Protein levels, which is out of scope for this example. Note that the LIVD file would NOT contain the local Ask at ORder entry questions (local codes 444 and 555), nor the calculated value for local code 777. CSF=Cerebrospinal Fluid. Vendor Analyte Code = 1099 (Total Protein CSF/Ur) is mapped in the LIS to:

• LIS Test Info = Result Code 111 - Result Name Protein, CSF Units mg/dL
• LIS Test Info = Result Code 222 - Result Name Protein, Random Urine Units mg/dL
• LIS Test Info = Result Code 333 - Result Name Protein, 24 Hour Urine Units mg/dL

LIVD Mapping Vendor Analyte Code = 1099 (Total Protein CSF/Ur) suggests:

• Based on vendor comment [comment], vendor result description [result] A, vendor specimen description [specimen] "CSF", LOINC axes => 2880-3
• Based on vendor comment [comment], vendor result description [result] B, vendor specimen description [specimen] "Urine", LOINC axes => 2888-6
• Based on vendor comment [comment], vendor result description [result] C, vendor specimen description [specimen] "24 hour Urine", LOINC axes => 21482-5

Consequently, most appropriate mapping would be:

• LIS Test Info = Result Code111 - Result Name Protein, CSF Units mg/dL
• LOINC Code = 2880-3 Protein [Mass/volume] in Cerebral spinal fluid
• LIS Test Info = Result Code 222 - Result Name Protein, Random Urine Units mg/dL
• LOINC Code = 2888-6 Protein [Mass/volume] in Urine
• LIS Test Info = Result Code 333 - Result Name Protein, 24 Hour Urine Units mg/dL
• LOINC Code = 21482-5 Protein [Mass/volume] in 24 hour Urine
• LIS Test Info = Result Code 444 - Result Name Hours of Collection Units Hours - calculated from values in 333 and 444
• LOINC Code = 13362-9 Collection duration of Urine - provided as AOE
• LIS Test Info = Result Code 555 - Result Name Total Volume 24 Hour Urine Volume Units mL
• LOINC Code = 3167-4 Volume of 24 hour Urine - provided as AOE
• LIS Test Info = Result Code 777 - Result Name Total Protein, 24 Hour Urine Rate Units g/24 Hr
• LOINC Code = 2889-4 Protein [Mass/time] in 24 hour Urine - calculated from values in 333, 444 and 555

Example #3 - Result Value Code

A manufacturer defined the following codes for an Immunoassay molecular antigen test:

• Positive
• Negative
• Invalid

The manufacture established the following SNOMED CT mappings for the result values:

• Positive = 260373001, “Detected”
• Negative = 260415000, “Not Detected”
• Invalid = 455371000124106, “Invalid result”