Health Language Blog

LOINC: A Better Path to Laboratory Data Exchange

Posted on 08/17/16

doctor_looking_through_microscope.jpgPart Three of our Terminology Standards series we introduced SNOMED CT as a comprehensive standard for exchanging clinical content in an accurate, meaningful way. In this installment, we explore use of LOINC for exchange of laboratory and clinical information.

Value-based care models demand more collaborative care delivery built on the timely sharing of critical patient information, such as labs, vital signs, or clinical documents. Because data is represented in different ways across local and disparate systems, healthcare organizations face notable challenges to sharing, exchanging, and aggregating data in an accurate, meaningful way.

Overcoming this challenge of semantic interoperability requires mapping of disparate test codes to a universal standard that every system can understand. This is where Logical Observation Identifiers Names and Codes (LOINC) comes into play. When lab and other clinical observations are mapped to this common language, critical information is more easily shared in support of population health and analytics initiatives.


LOINC was introduced in 1994 by the Regenstrief Institute as a free, universal standard for laboratory and clinical observations. Encompassing a set of identifiers, names, and codes, LOINC is the largest and most widely adopted global standard for identifying tests and observations.

The non-profit Regenstrief Institute, an affiliate of the Indiana School of Medicine, owns and maintains LOINC. More than 172 countries use the standard today, including large-scale health information exchanges in Hong Kong, Italy, the Philippines, Spain, Singapore, and Korea.


Many associate LOINC with laboratory terminology, but it also contains a dictionary of radiologic terms, including a limited number of clinical observations and codes for various assessments and surveys. It is a HIPAA-required standard for the transmission of laboratory data, and is required for meaningful use as well as quality reporting measures.

LOINC encompasses essentially anything you can test, measure, or observe about a patient and is generally divided into two major content divisions: laboratory and clinical:

Laboratory focuses on specimens covering chemistry, hematology, serology, microbiology (including parasitology and virology), and toxicology, as well as categories for cell counts, antibiotic susceptibilities, and more.

Clinical focuses on patient (non-specimen) tests, measurements, and observations including vital signs, hemodynamics, intake/output, EKG, obstetric ultrasound, cardiac echo, urologic imaging, gastroendoscopic procedures, pulmonary ventilator management, radiology studies, clinical documents, selected survey instruments (e.g., Glasgow Coma Score, PHQ-9 depression scale, CMS-required patient assessment instruments), and more.


LOINC codes represent either a discrete measurement or a “collection” of measurements (for example, a single lab test or a panel of lab tests). They distinguish a given observation (test ordered/reported, survey question, clinical document) across six dimensions called parts:

  • Component (Analyte): The substance or entity being measured or observed.
  • Property: The characteristic or attribute of the analyte.
  • Time: The interval of time over which an observation was made.
  • System (Specimen): The specimen or thing upon which the observation was made.
  • Scale: How the observation value is quantified or expressed: quantitative, ordinal, nominal.
  • Method: (Optional) A high-level classification of how the observation was made. Only necessary when the technique affects the clinical interpretation of the results.

For example, here is a breakdown of the LOINC name for a manual count of white blood cells in cerebral spinal fluid specimen, which is represented by LOINC code 806-0:

  1. Component (Analyte): Leukocytes (white blood cells)
  2. Property: NCnc (Number concentration)
  3. Time: Pt (Point in time)
  4. System (Specimen): CSF (Cerebral spinal fluid)
  5. Scale: Qn (Quantitative)
  6. Method: Manual Count

LOINC in Action

In an electronic transmission of laboratory results from a regional lab to a provider, LOINC records the question, and SNOMED records the answer. The transmission will include the LOINC code indicating the test that was performed and a SNOMED code to report the finding from that test. For example, the LOINC code 4548-4 Hemoglobin A1c/Hemoglobin total in Blood might be reported together with SNOMED code 444751005 | Hemoglobin A1c above reference range (finding). Critical to fully leveraging the power of these codes is a system that allows the two standards—LOINC and SNOMED—to communicate with one another.

Most laboratory and clinical systems today are sending data using the HL7 version 2 messaging standard. The example below demonstrates how a LOINC code identifies the question and a SNOMED CT code represents the answer in an HL7 message:

LONC blog.png


To sum up, LOINC is the clear industry standard for describing laboratory testing and transmitting laboratory orders electronically. Healthcare organizations need systems in place to accurately map local and disparate laboratory data to LOINC to improve semantic interoperability.


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Topics: Standard terminologies, LOINC, data normalization

About the Author

Monica Morris has over 10 years of experience in Health Information Management and Health Informatics. As a Clinical Application Analyst with the Health Language Professional Services team, Monica provides mapping and translation services related to RxNorm, LOINC, and other terminologies, including ICD-9, ICD-10, CPT, and SNOMED CT. She is very knowledgeable in standard quality measures and the development of code sets related to those measures. Her skills are utilized in developing and delivering application end training to clients and providing subject matter expertise support for all clients. She specializes in data normalization for drug and lab projects, and offers consulting and analysis on mapping and translation of client local terminology.