# LOINC Code

Key: `identity.medical.loinc`

Logical Observation Identifiers Names and Codes — universal standard for identifying lab observations and clinical measurements. Format: 1-5 digits, hyphen, single check digit.

Page: <https://meridian.online/docs/projects/finetype/types/identity/medical/loinc>

Samples: `2951-2`, `718-7`, `4548-4`, `14749-6`, `2345-7`

## Background

### Origin

LOINC stands for Logical Observation Identifiers Names and Codes.[[1]](https://en.wikipedia.org/wiki/LOINC) Dr. Clement McDonald created LOINC at the Regenstrief Institute in 1994.[[2]](https://www.regenstrief.org/article/mcdonald-honored-for-pioneering-medical-informatics-improving-health-worldwide/) The Regenstrief Institute is a US nonprofit medical research organisation.[[1]](https://en.wikipedia.org/wiki/LOINC) LOINC was created in response to the demand for an electronic clinical care and management database.[[1]](https://en.wikipedia.org/wiki/LOINC) LOINC continues to be managed by the Regenstrief Institute.[[2]](https://www.regenstrief.org/article/mcdonald-honored-for-pioneering-medical-informatics-improving-health-worldwide/) The US National Library of Medicine supports the ongoing development of LOINC through a contract arrangement.[[3]](https://www.nlm.nih.gov/research/umls/loinc_main.html)

Each LOINC entry is assigned a unique code when it is registered.[[1]](https://en.wikipedia.org/wiki/LOINC) The LOINC code is a numeric code with a Mod 10 check digit.[[4]](https://implementer.digitalhealth.gov.au/standards/users-guide-12-c-calculating-mod-10-check-digits-v2023)

### Use

LOINC is one of the standards used in U.S. Federal Government systems for the electronic exchange of clinical health information.[[1]](https://en.wikipedia.org/wiki/LOINC) In 1999 the HL7 Standards Development Organization identified LOINC as a preferred code set for laboratory test names.[[1]](https://en.wikipedia.org/wiki/LOINC) In HL7 FHIR, the URI http://loinc.org identifies LOINC codes.[[5]](https://hl7.org/fhir/R4/loinc.html) For comparison purposes, FHIR treats LOINC codes as not case sensitive.[[5]](https://hl7.org/fhir/R4/loinc.html)

The LOINC Users' Guide lists 14 terms known to have invalid check digits.[[4]](https://implementer.digitalhealth.gov.au/standards/users-guide-12-c-calculating-mod-10-check-digits-v2023) Treat a failed check digit as a reason to look the code up rather than as proof the value is wrong. (Meridian's view) LOINC Answer String IDs, such as LA11165-0, are also valid LOINC codes in FHIR.[[5]](https://hl7.org/fhir/R4/loinc.html) LOINC Part codes carry an LP prefix and a mod-10 check digit, as in LP31755-9.[[5]](https://hl7.org/fhir/R4/loinc.html) A column of LOINC codes from a FHIR feed may therefore mix plain numeric codes with LA or LP identifiers, so check for letter prefixes before applying a digits-only pattern. (Meridian's view)

### Where you'll meet it

A Regenstrief Institute article says LOINC is used in 193 countries and is available in 20 languages.[[2]](https://www.regenstrief.org/article/mcdonald-honored-for-pioneering-medical-informatics-improving-health-worldwide/) In Synthea's synthetic patient data, the Code column of observations.csv holds the observation or lab code from LOINC.[[6]](https://github.com/synthetichealth/synthea/wiki/CSV-File-Data-Dictionary)

## Sources

1. [LOINC - Wikipedia](https://en.wikipedia.org/wiki/LOINC) — secondary source
2. [Clement McDonald, M.D., honored for his pioneering work in medical informatics at Regenstrief Institute to improve health in Indiana and around the world - Regenstrief Institute](https://www.regenstrief.org/article/mcdonald-honored-for-pioneering-medical-informatics-improving-health-worldwide/) — organisation
3. [UMLS - LOINC](https://www.nlm.nih.gov/research/umls/loinc_main.html) — organisation
4. [Users' Guide: 12 C - Calculating Mod 10 Check Digits v2023](https://implementer.digitalhealth.gov.au/standards/users-guide-12-c-calculating-mod-10-check-digits-v2023) — secondary source
5. [Loinc - FHIR v4.0.1](https://hl7.org/fhir/R4/loinc.html) — documentation
6. [CSV File Data Dictionary](https://github.com/synthetichealth/synthea/wiki/CSV-File-Data-Dictionary) — dataset