The Language of Healthcare: Exploring LOINC
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Welcome back to our blog series on essential healthcare terminologies that are transforming data management and patient care. So far, we’ve covered SNOMEDCT, a comprehensive standard for clinical terminology, and ICD10CM, a vital classification system for coding health conditions and procedures. This week, we shift our focus to LOINC (Logical Observation Identifiers Names and Codes), a universal standard for identifying health measurements, observations, and documents.
In this post, we'll demystify LOINC, explaining its role in ensuring consistent communication of laboratory tests, clinical observations, and diagnostic reports across healthcare systems. We'll explore how to read, search, and analyze LOINC codes accurately, provide an overview of content modeling, maintenance, and version updates, and help users gain confidence and access resources for handling LOINC-based tasks effectively.
Don’t forget to explore TermHub’s public ICD10CM project to get hands-on experience with this critical terminology. Stay with us throughout this series as we continue to unpack the healthcare terminologies that matter most. Follow TermHub on LinkedIn to get timely insights that can help you stay at the forefront of healthcare data management.
What is LOINC?
Developed and maintained by the Regenstrief Institute, LOINC (Logical Observation Identifiers Names and Codes) is a standardized nomenclature used for representing laboratory tests, clinical measurements, and diagnostic observations. It provides a structured method to encode and exchange health data consistently across healthcare systems.
LOINC serves as a unifying standard, facilitating interoperability among electronic health records (EHRs), laboratory information systems, and clinical decision support tools. By standardizing health observations and measurements, LOINC ensures accurate clinical documentation, seamless data sharing, and improved healthcare outcomes across diverse healthcare environments.
Widely adopted in the United States, LOINC is also used internationally for standardized reporting and data exchange, supporting global interoperability among laboratories, hospitals, research institutions, and public health organizations.
What does a LOINC Concept look like?
Each LOINC concept includes a unique identifier (LOINC code), structured names (fully specified names), and detailed attributes organized along six axes: component, property, timing, system, scale, and method. These attributes precisely define laboratory tests, clinical measurements, and diagnostic observations, ensuring consistent representation across healthcare systems.
Below are two visual representations of commonly used LOINC concepts, along with links to additional examples available in TermHub. These example concepts illustrate common clinical and laboratory scenarios encountered in healthcare settings.
Examples of LOINC Concepts
8310-5 - Body temperature
2345-7 - Glucose [Mass/volume] in Serum or Plasma
4548-4 - Hemoglobin A1c/Hemoglobin.total in Blood
2160-0 - Creatinine [Mass/volume] in Serum or Plasma
10839-9 - Troponin I.cardiac [Mass/volume] in Serum or Plasma
2085-9 - Cholesterol in HDL [Mass/volume] in Serum or Plasma
89263-8 - Systolic blood pressure
72166-2 - Tobacco smoking status
94016-3 - Depression screening report
72253-8 - CT Chest and Abdomen and Pelvis WO contrast
What clinical use cases does LOINC best support?
LOINC provides standardized terminology for laboratory tests, clinical observations, and diagnostic measurements, enabling consistent communication and interoperability across healthcare systems. It supports critical clinical workflows by ensuring accurate data reporting, interpretation, and exchange.
Top Clinical Use Cases:
Laboratory Results Reporting: Standardizing lab test results (e.g., blood glucose, cholesterol) across systems.
Radiology Reporting: Ensuring uniform reporting of imaging studies (X-rays, MRIs, CT scans).
Clinical Documents and Structured Data Exchange: Facilitating exchange of structured clinical notes, discharge summaries, and continuity of care documents (CCD).
Public Health Reporting: Supporting standardized reporting for disease surveillance and immunization tracking.
Genomics and Precision Medicine: Standardizing genetic test results for accurate communication in clinical genomics.
Clinical Research and Trials: Ensuring consistency in data exchange for clinical trials and meta-analyses.
Quality Reporting and Measurement: Standardizing quality metrics reporting for performance assessments.
Home Health Monitoring and Remote Patient Management: Standardizing data from remote monitoring devices (e.g., blood pressure monitors, glucose meters) for seamless integration into EHRs
LOINC promotes accurate data sharing, interoperability, and improved patient outcomes across diverse healthcare settings.
How granular are LOINC codes in representing clinical information?
LOINC achieves exceptional granularity through structured representation of clinical observations along six dimensions: component, property, timing, system, scale, and method. These dimensions enable precise documentation and interpretation of clinical measurements.
An illustrative example of this granularity is the differentiation based on Anatomical Measurement Site:
General measurement: Body temperature (LOINC 8310-5)
Specific measurements:
Oral temperature (LOINC 8331-1)
Axillary temperature (LOINC 8328-7)
Tympanic membrane temperature (LOINC 8333-7)
Other examples demonstrating LOINC granularity include:
Anatomical Specificity:
Systolic blood pressure (LOINC 8480-6)
Middle finger arteries - left Systolic blood pressure (LOINC 8563-9)
Method of Measurement:
Troponin I.cardiac [Mass/volume] in Serum or Plasm (LOINC 10839-9)
Troponin T.cardiac [Mass/volume] in Serum or Plasma by High sensitivity method (LOINC 67151-1)
Timing of Observation:
Glucose [Mass/volume] in Blood (LOINC 2339-0)
Fasting glucose [Moles/volume] in Blood (LOINC 76629-5)
This structured granularity ensures accurate clinical interpretation, supports interoperability, and enhances data quality across healthcare settings.
What are the basic components of LOINC?
A LOINC release consists of several key components that provide the structure for managing and using clinical and laboratory observations. These components ensure LOINC's utility for data exchange and interoperability in healthcare systems. Here is a basic overview of a LOINC release:
LOINC Code: The unique identifier for a specific test or observation (e.g., "2340-8" for "Glucose [Mass/volume] in Blood by Automated test strip").
LOINC Table
The core component of a LOINC release is the LOINC table, which contains all LOINC codes, their attributes, and metadata. It is a comprehensive file used to store and reference clinical observations and lab tests.
Key Fields in the LOINC Table
LOINC Code
Component: The analyte or observation being measured (e.g., "Glucose").
Property: The type of quantity being measured (e.g., "Mass concentration").
Time Aspect: When the measurement is taken (e.g., "Point in time (spot)").
System: The biological system or specimen being measured (e.g., "Blood").
Scale: The type of scale used to report results (e.g., "Semiquantitative").
Method: The method used to perform the measurement (e.g., "Test strip automated").
Various Description Fields:
Short Name: Glucose Bld Strip.auto-mCnc
Display Name: Glucose Auto test strip (Bld) [Mass/Vol]
Long Common Name: Glucose [Mass/volume] in Blood by Automated test strip
Additional metadata including status, example answers, example units, etc.
Answer Lists
LOINC provides standardized sets of answers, called answer lists, that can be used for observations that have multiple possible responses. These answer lists are referenced by LOINC codes when the test or observation result is reported in a categorical format.
LOINC Panels and Forms
Panels are collections of individual LOINC codes that represent a group of related observations or tests often performed together. Forms represent templates that might be used for specific assessments or questionnaires.
Examples of Panels:
Vital signs panel: A collection of LOINC codes for body temperature, heart rate, respiratory rate, and blood pressure.
Complete Blood Count (CBC) panel: Includes multiple LOINC codes for red blood cells, white blood cells, hemoglobin, and platelets.
LOINC GROUPS: LOINC groups are collections of related LOINC codes that can be grouped together to support a common use case. These groups are a work in progress and require validation prior to implementation but can be a good starting point.
Example: A group for all glucose tests, regardless of specimen type or method
What is the release schedule of LOINC?
LOINC follows a structured release schedule to ensure the terminology remains current with the latest medical practices and technological advancements. LOINC releases occur biannually, typically in February and August, to provide updates that include new codes, revisions to existing codes, and other enhancements to the system. Each release undergoes a rigorous process of review and validation to maintain the accuracy, relevance, and utility of LOINC codes across diverse healthcare settings.
Each new release includes contributions from the global community of LOINC users and stakeholders, who submit requests for new codes or suggest modifications to existing ones. To access the latest and previous releases of LOINC, visit the LOINC Download site.
How do identifiers work in LOINC?
LOINC identifiers are unique codes assigned to each concept in the LOINC database, representing a specific clinical observation, measurement, or document. These identifiers, also known as LOINC codes, are composed of a numeric string followed by a check digit and are formatted in a way that ensures they are both unique and unambiguous. The LOINC code itself does not carry intrinsic semantic meaning within its digits—LOINC identifiers are essentially "dumb" numbers designed to provide a unique reference without embedding meaning in the code structure.
However, while the numeric portion of the identifier is not semantically meaningful, understanding how LOINC identifiers work involves knowing the structure and format used to create them.
Example: Understanding a LOINC Identifier (using 2345-7)
2345 - The main numeric portion of the identifier. This is a unique number assigned by the Regenstrief Institute, which maintains the LOINC database. It represents a specific clinical test or observation, such as "Glucose [Mass/volume] in Serum or Plasma" This portion does not have a built-in semantic meaning; it's simply an identifier.
- (Hyphen) - A separator that distinguishes the main segment of the code from the check digit. This separator is used consistently in all LOINC codes to ensure clarity and to prevent errors during manual data entry or electronic data exchange.
7 - The check digit, which is calculated using the Mod 10 algorithm. This digit is used to verify that the identifier has been correctly transmitted or entered. The check digit helps detect common errors such as transposed digits or mistyped codes, enhancing the reliability and accuracy of data exchange.
What type of knowledge graph does LOINC utilize?
LOINC does not specifically utilize a formal knowledge graph in its standard releases. However, LOINC can be integrated into knowledge graph systems to represent relationships between clinical and laboratory concepts. This approach is often employed in health informatics and clinical decision support systems to enhance data interoperability, linking LOINC codes with other vocabularies such as SNOMEDCT, ICD-10, and FHIR resources.
LOINC’s Conceptual Structure for Knowledge Graphs
While LOINC itself is a comprehensive set of observation codes, its structure can be viewed as a semantic network or ontology of terms, which can serve as a foundation for knowledge graph integration. The components of LOINC, such as its codes, properties, systems, and methods, represent nodes and relationships in a knowledge graph.
Concept Nodes: Each LOINC code represents a unique concept, such as a specific laboratory test or clinical observation. For example: "2340-8" → Glucose [Mass/volume] in Blood by Automated test strip.
Attributes/Properties: LOINC concepts are defined using several key attributes that could form relationships between nodes in a knowledge graph:
Component: The analyte or observation being measured (e.g., "Glucose").
Property: The type of quantity being measured (e.g., "Mass concentration").
Time Aspect: When the measurement is taken (e.g., "Point in time (spot)").
System: The biological system or specimen being measured (e.g., "Blood").
Scale: The type of scale used to report results (e.g., "Semiquantitative").
Method: The method used to perform the measurement (e.g., "Test strip automated").
Relationships: LOINC codes can be related to other ontologies, terminologies, and datasets, forming relationships such as:
LOINC Ontology: A representation of LOINC (currently just laboratory) in the SNOMEDCT concept model. This is an effort that is currently under development and would provide the knowledge graph for LOINC.
Hierarchical Relationships: The multi-axial hierarchy of LOINC organizes codes into categories (like clinical vs. laboratory observations), which can be represented as hierarchical relationships in a knowledge graph.
Knowledge Graph Applications for LOINC
● Data Integration: LOINC codes can be used in knowledge graphs that integrate multiple clinical terminologies, such as linking lab test results (LOINC) with diagnoses (ICD-10) and treatments (CPT).
● Clinical Decision Support: Knowledge graphs using LOINC help power clinical decision-making by associating lab results with specific clinical guidelines or actions.
● Interoperability: By mapping LOINC codes in knowledge graphs, healthcare systems can achieve semantic interoperability, ensuring that data from different systems are comparable and consistent.
Example: FHIR and Knowledge Graphs
LOINC is commonly used in conjunction with FHIR (Fast Healthcare Interoperability Resources), which structures healthcare data in a format that can easily integrate into a knowledge graph. A FHIR-based knowledge graph might include:
● LOINC codes for lab tests.
● SNOMEDCT or ICD-10 codes for diagnoses.
● Relationships between clinical entities (e.g., lab results impacting treatment decisions).
In summary, while LOINC itself is not explicitly a knowledge graph, its structured vocabulary can be embedded into knowledge graphs to enhance clinical data interoperability and reasoning in healthcare systems.
Can LOINC be extended?
LOINC itself cannot be directly customized by individual organizations or users. LOINC is a standardized set of codes developed and maintained by the Regenstrief Institute, a non-profit organization responsible for ensuring that LOINC remains a universal and consistent standard for representing clinical data. Customization at the user or organizational level would undermine the interoperability and consistency that LOINC is designed to provide across different healthcare systems and settings.
However, while direct customization of LOINC codes is not permitted, the system does allow for flexibility in terms of requesting changes or proposing new codes to address specific needs. Users who identify gaps or find that certain concepts are not adequately represented in LOINC can suggest modifications or request new codes. The Regenstrief Institute regularly reviews these requests and updates the LOINC database biannually to reflect changes and new requirements in healthcare.
Who Maintains LOINC?
LOINC is maintained by the Regenstrief Institute, a non-profit medical research organization based in Indianapolis, Indiana, USA. The Regenstrief Institute, founded in 1969, is dedicated to improving health and healthcare through innovative research in biomedical informatics, aging, and health services. Since creating LOINC in 1994, the institute has been responsible for its ongoing development, ensuring it remains a global standard for coding health measurements, observations, and documents.
LOINC is made available as a free, open-access resource to encourage its broad adoption and use worldwide. The Regenstrief Institute provides access to LOINC through its official website, where users can download the latest version of the database, along with release notes, user guides, and other supporting materials.
Resources for Learning More About LOINC
LOINC Website: The official website, loinc.org, is the primary resource for accessing the LOINC database, user guides, release notes, submission forms, and other resources.
LOINC YouTube Channel: The LOINC YouTube channel provides webinars, tutorials, and presentations about using LOINC and understanding its structure.
LOINC Documentation: Extensive documentation, such as the LOINC Users' Guide, offers detailed information on how to use LOINC codes effectively, including examples, guidelines, and use cases.
LOINC Conferences and Meetings: Regular events, including conferences, workshops, and committee meetings, are hosted by the Regenstrief Institute. These gatherings provide opportunities to learn about the latest updates, share experiences, and contribute to LOINC's development. More information on upcoming events can be found on the LOINC Events page.
Online Community and Forums: The LOINC Forums provide a platform for users to discuss best practices, share feedback, and stay connected with the LOINC community.
What is the History of LOINC?
LOINC was initially created to address the need for a standardized way to identify clinical observations, laboratory tests, and measurement results across different healthcare settings. Developed in 1994 by the Regenstrief Institute, a leading non-profit medical research organization, LOINC was designed to facilitate the exchange and interoperability of clinical data, ensuring that health information could be easily understood and utilized, regardless of the specific systems or technologies in use.
Origins and Development of LOINC
The development of LOINC began in the early 1990s when healthcare providers, laboratories, and electronic health record (EHR) systems faced challenges in exchanging data due to the lack of a common standard. The Regenstrief Institute, under the leadership of Dr. Clement McDonald, recognized this critical need and initiated the LOINC project to create a universal coding system for identifying clinical observations and laboratory tests. The initial version of LOINC focused on laboratory test codes, which quickly gained adoption due to their ability to standardize the representation of test results across different institutions and systems.
Over the years, LOINC expanded beyond laboratory tests to include other types of clinical data, such as vital signs, radiology procedures, clinical documents, and medical surveys. This growth was driven by the increasing demand for comprehensive data interoperability in healthcare, supported by the growing adoption of EHR systems and health information exchanges (HIEs).
What challenges come with using LOINC?
While LOINC is a powerful tool for standardizing the exchange of clinical data and enhancing interoperability, its use can come with several challenges. These challenges are often related to the complexity of implementing a comprehensive coding system across diverse healthcare settings, the need for ongoing maintenance and updates, and the learning curve associated with understanding and correctly applying LOINC codes. For many organizations, the successful adoption of LOINC requires careful planning, resource allocation, and ongoing education to overcome these hurdles.
Common Challenges with Using LOINC
Implementation Complexity: Integrating LOINC into existing electronic health record (EHR) systems and laboratory information systems (LIS) can be technically complex. Organizations may need to map their existing codes to LOINC, which can be time-consuming and require specialized knowledge.
Resource Intensity: Implementing and maintaining LOINC requires dedicated resources, including skilled personnel for mapping and ongoing updates. Smaller organizations or those with limited resources may find it challenging to keep up with the biannual updates and changes to the LOINC database.
Training and Education: Staff members need training to understand how to use LOINC codes correctly. Misunderstandings or lack of knowledge about LOINC’s structure and proper usage can lead to errors in data entry and reporting, potentially affecting data quality and interoperability.
Keeping Up with Updates: LOINC is updated twice a year, and organizations must stay current with these changes to ensure accurate data exchange and reporting. This requires consistent monitoring and adaptation to incorporate new codes, retire outdated ones, and understand revisions.
Mapping Challenges: Mapping local codes or proprietary coding systems to LOINC can be difficult, especially when there is no direct equivalent LOINC code. This may result in the need for manual mapping, which is labor-intensive and prone to errors.
Variation in Adoption: Not all healthcare organizations or systems use LOINC, leading to inconsistencies in data exchange. This variation in adoption can pose interoperability challenges, especially when sharing data across different platforms or regions.
Handling Granularity: LOINC codes can be very granular, which is beneficial for precision but may also complicate data management. Choosing the appropriate level of detail for different clinical scenarios can be challenging and may require expert judgment.
Navigating International Differences: While LOINC is used internationally, variations in healthcare practices, languages, and regulatory requirements can complicate its adoption and consistent use across different countries.
How do I access and what are the licensing restrictions for LOINC?
LOINC is made freely available to support the interoperability of health data worldwide. In the United States, LOINC is distributed under a free license that allows users to download, use, and implement the codes without any cost. However, while there are generally no licensing fees for using LOINC, there are some terms and conditions that users must adhere to.
Licensing Restrictions in the US
Free to Use: LOINC is available for free to anyone who wishes to use it for healthcare data exchange, research, education, and public health purposes.
Acknowledgment Requirement: Users must acknowledge the Regenstrief Institute in their product or service documentation if they incorporate LOINC codes.
No Modification of Codes: Users are not allowed to modify the actual LOINC codes or names to maintain their integrity and ensure consistent use across all healthcare systems.
Commercial Use: While LOINC is free for both non-commercial and commercial use, users must adhere to the terms of the LOINC license agreement provided by the Regenstrief Institute.
How to Access LOINC
To access LOINC, you can visit the official LOINC website and download the latest version of the LOINC database, along with all relevant documentation, user guides, and updates.