By Eric Andrew Kristof, RN, CAHIMS | Healthcare IT Professional | HIMSS Arkansas Chapter Member
About This Series: The HIMSS Word of the Day is a running blog series drawing from the HIMSS Dictionary of Health Information and Technology Terms, Acronyms, and Organizations, 6th Edition (2025) — the authoritative reference for healthcare IT professionals and the primary study resource for CAHIMS and CPHIMS certification. Each post paraphrases the term in plain language, grounds it in real-world healthcare IT context, and adds a bedside nursing perspective you won’t find in a textbook.
📖 The Term: Logical Observation Identifiers Names and Codes (LOINC)
Source: HIMSS Dictionary of Health Information and Technology Terms, Acronyms, and Organizations, 6th Edition (2025)
🔍 Plain-Language Definition
LOINC is a universal coding system for laboratory tests and clinical observations. It gives each distinct test or measurement a standard code and name, so that a result sent from one system can be correctly understood by another.
The HIMSS Dictionary describes LOINC as universal identifiers for lab and clinical observations, measurements, and documents. Its coverage reaches well beyond the laboratory, including vital signs, hemodynamic measurements, intake and output, EKG findings, obstetric and cardiac ultrasound, endoscopy, ventilator management, and standardized survey instruments. LOINC was started in 1994 by Clem McDonald at the Regenstrief Institute, which still maintains it and makes it freely available.
Every LOINC term is defined by up to six parts, which together distinguish tests that might otherwise share a name:
| Part | What It Captures | Example: Serum Glucose |
|---|---|---|
| Component | What is being measured | Glucose |
| Property | The kind of quantity | Mass concentration |
| Time | Point in time or over an interval | Point in time |
| System | The specimen or body system | Serum or plasma |
| Scale | Quantitative, ordinal, nominal, or narrative | Quantitative |
| Method | How it was measured, when it matters | Not specified |
The result is a code such as 2345-7, which identifies a glucose concentration in serum or plasma. Vital signs have LOINC codes too, such as 8867-4 for heart rate and 8480-6 for systolic blood pressure.
⚠️ Exam Alert: LOINC identifies what was measured or asked: the test, observation, or document type. SNOMED CT describes clinical findings, diagnoses, and procedures, and it is often used for coded answers to LOINC questions, such as an organism identified in a culture. CPT codes procedures, including lab tests, for billing. RxNorm names medications. A question asking which standard to use for lab result identification points to LOINC.
🌐 Why It Matters: Real-World Healthcare IT Context
Every lab and every EHR has its own local names and codes for tests. One system’s “GLU” may be another’s “Glucose, serum,” and a single hospital may have several glucose tests that differ by specimen, method, or timing. Without a shared code, a receiving system cannot reliably tell which test it is looking at, trend results over time, or apply decision support to outside data.
LOINC solves that by giving each distinct test a universal identifier that travels with the result. Federal policy builds on it: USCDI points to LOINC for laboratory tests, vital signs, and clinical note types, and certified health IT must be able to exchange those data elements using it. LOINC also underpins quality measures, public health reporting, and research data sets that combine results from many organizations.
LOINC is also global. According to the Regenstrief Institute, thousands of organizations in nearly every country use it, which makes it one of the few health data standards that works the same way across national borders. That matters for research collaborations, international reporting, and vendors that build lab and EHR products for many markets.
LOINC covers orders as well as results. A lab panel that a provider orders can have its own LOINC code, and each component result inside the panel has another. That distinction helps receiving systems understand both what was requested and what came back, which is useful when results arrive from outside labs and need to be filed in the right place.
LOINC’s document ontology also matters. Clinical note types, such as a discharge summary or a history and physical, have LOINC codes, which is how exchanged documents and FHIR resources identify what kind of note they contain.
Common LOINC challenges:
- Local test codes mapped to the wrong LOINC term, especially for specimen or method
- Mappings that are never updated when labs change instruments or tests
- Flowsheet rows and assessment tools that have no standard code at all
- Reference labs and hospitals using different LOINC codes for similar tests
- Mapping work treated as a one-time project instead of ongoing maintenance
Strengths of mature LOINC programs:
- Laboratory and informatics teams that jointly own test-to-LOINC mapping
- Mapping reviewed whenever tests, instruments, or reference labs change
- Vital signs and key nursing observations mapped to standard LOINC codes
- Use of LOINC alongside SNOMED CT for coded results
- Validation of outgoing data against USCDI and exchange partner requirements
🏥 The Nurse’s Perspective: Clinical, Bedside, & Workflow
Nurses rarely type a LOINC code, but nearly every number they chart may depend on one.
At the Bedside
Each vital sign a nurse records, including heart rate, blood pressure, respiratory rate, temperature, oxygen saturation, height, and weight, is a clinical observation that can carry a LOINC code. When those flowsheet rows are mapped correctly, the values can appear in the patient portal, travel to the next provider, feed early warning scores, and count toward quality measures.
When a unit builds a custom row for a common measurement instead of using the standard one, the data still looks fine on the screen but may never leave the chart in a usable form.
In Clinical Workflow
Point-of-care testing is a practical example. A bedside glucose or a rapid test entered by a nurse needs to be documented as the right test so that it is interpreted correctly alongside laboratory results. Mixing point-of-care and lab values under the wrong code can distort trends and decision support.
Standardized assessments matter too. Many screening tools and survey instruments, from depression screens to functional assessments, have LOINC codes for their questions and scores. Using those standard instruments, rather than locally modified versions, keeps nursing assessment data comparable and reusable.
In EHR Implementation (Go-Live Perspective)
During an Epic implementation, lab build teams map orderable tests and result components to LOINC, and clinical build teams map flowsheet rows for vital signs and other observations. Those mappings are tested through lab interfaces and exchange validation before Go-Live, and errors found later can be difficult to unwind.
End-user support analysts often see mapping problems as clinical complaints: a result that does not trend with earlier values, an outside lab result that lands in the wrong place, or vital signs missing from a patient’s shared summary. Recognizing these as terminology issues, and routing them to the lab or interoperability analyst, protects the integrity of the data.
🎓 CAHIMS / CPHIMS & HIMSS Perspective
CAHIMS Exam Domain Mapping
LOINC is a frequently tested terminology standard on the CAHIMS exam:
| CAHIMS Domain | How LOINC Appears |
|---|---|
| Healthcare & Technology Environments | USCDI requirements; terminology standards and the organizations that maintain them |
| Clinical Informatics | Coded lab results and observations; vital signs; standardized assessments; decision support on coded data |
| Healthcare Information & Systems Management | Lab interfaces; local-to-standard code mapping; terminology maintenance; data quality |
| Management & Leadership | Ownership of terminology governance; supporting analytics, quality, and research |
Key Terms to Know Alongside LOINC
- SNOMED CT — the clinical terminology for findings, diagnoses, and procedures, often used for coded result values
- CPT (Current Procedural Terminology) — the code set used to bill for procedures and services, including lab tests
- RxNorm — the National Library of Medicine’s standard naming system for medications
- USCDI — the federal list of data classes and elements that relies on LOINC for labs and vital signs
- Semantic Interoperability — exchange in which the meaning of data is preserved between systems
- Terminology Mapping — linking local codes to standard codes so data can be exchanged and compared
HIMSS Organizational Position
HIMSS treats standards-based, semantically interoperable data as a foundation of digital health and supports terminology adoption through its interoperability policy work. Members can find data quality and standards guidance through the HIMSS Resource Center and Global Health Conference programming.
🔗 Explore Further: External References
- Regenstrief Institute — LOINC https://www.regenstrief.org/real-world-solutions/loinc/
- LOINC — Official Site https://loinc.org/
- National Library of Medicine — LOINC in the UMLS https://www.nlm.nih.gov/research/umls/loinc_main.html
- ONC — U.S. Core Data for Interoperability (USCDI) https://isp.healthit.gov/united-states-core-data-interoperability-uscdi
- SNOMED International — SNOMED CT https://www.snomed.org/
- ONC — Interoperability Standards Platform https://isp.healthit.gov/
Term source: HIMSS Dictionary of Health Information and Technology Terms, Acronyms, and Organizations, 6th Edition (2025). All definitions in this series are paraphrased for editorial purposes. Readers are encouraged to consult the primary source for exact language.
Eric Andrew Kristof, RN, CAHIMS is a Healthcare IT professional and HIMSS Arkansas Chapter member based in Hot Springs Village, AR, with hands-on Epic Go-Live experience and a diverse healthcare and IT background. He writes at kristof.org at the intersection of clinical care and healthcare technology.
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