LOINC

Key facts

Maintained by

Regenstrief Institute, Indianapolis

Created

1994

Cost

Free to use under the LOINC license

Code format

Numeric code with a check digit after a hyphen

Name parts

Component, property, time, system, scale and method

What is LOINC?

Laboratories and health systems have long named the same test in different ways, so a glucose result from one hospital could not be reliably matched to a glucose result from another. LOINC solves that by giving each distinct test or observation a universal code and a formal name.

The Regenstrief Institute created LOINC in 1994 and maintains it with input from laboratories, health systems, government agencies and standards bodies. It is free to use. Beyond lab tests, LOINC codes clinical observations such as vital signs, standardized assessment instruments and questionnaires, and the types of clinical documents exchanged between systems.

How a LOINC code is defined

Each LOINC term has a numeric code with a check digit, such as 2345-7, and a fully specified name built from six parts:

Two tests that differ in any of these parts receive different codes, which is why one analyte can have many LOINC codes.

• Component: what is measured, such as glucose.
• Property: the kind of quantity, such as mass concentration.
• Time aspect: a point in time or an interval, such as a 24-hour collection.
• System: the specimen or thing observed, such as serum or plasma.
• Scale: quantitative, ordinal, nominal or narrative.
• Method: how the result was obtained, when that changes its meaning.

Why LOINC matters

LOINC is what makes lab data comparable across organizations:

• Federal health IT certification and the United States Core Data for Interoperability (USCDI) name LOINC for laboratory tests, so lab results in EHRs and exchanged records are commonly LOINC-coded.
• Real-world evidence studies and quality measures rely on LOINC codes to pull the same lab value, such as hemoglobin A1c, across many health systems.
• Electronic laboratory reporting to public health agencies uses LOINC to identify the test performed.
• Results are typically paired with UCUM units and, for coded answers, SNOMED CT concepts.

LOINC vs CPT

A CPT code on a claim shows that a lab test was billed. A LOINC code in a lab result identifies exactly which test was run and lets the result value be interpreted. Claims data show testing volume, while LOINC-coded clinical data show the results themselves. The two code sets are not interchangeable and do not map one to one.