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Logical Observation Identifiers Names and Codes (LOINC) is a standardized coding system for laboratory and clinical tests, procedures, observations, surveys, and corresponding results.


All LOINC source information is obtained from the following:

1. LOINC Website that is supported by the Regenstrief Institute:

  • LOINC Table Core (Observations and Measurements)
  • LOINC Answers
  • LOINC Multiaxial Hierarchy
  • LOINC Document Ontology
  • LOINC Panels and Forms
  • LOINC Groups
  • LOINC to SNOMED mapping
  • LOINC Replacement Mapping

2. The National Library of Medicine (NLM) Website:

  • LOINC To CPT4 Mapping

3. LOINC Users' Guide:

  • Manual table of LOINC Classes

Concept Names

  • Values of a “long_common_name” field are considered to be preferred terms for concept names.
  • Values of “consumer_name”, “shortname” and “relatednames2” fields reside in the CONCEPT_SYNONYM table as synonyms.

Standard Concepts

Source Concept TypeStandard Concept
LOINC Observations and MeasurementsStandard
LOINC AnswersStandard
LOINC HierarchyClassification
LOINC ClassesClassification
LOINC CategoriesClassification
LOINC GroupsClassification

Domains and Concept Classes

LOINC Concepts are located in such domains as “Observation”, “Measurement”, or “Meas Value”.

Previously all concepts with a LOINC property of “classtype” with values “1” and “2” were considered to be Measurements. However, an initial analysis of such extended LOINC properties as “property”, system”, “scale_type”, “class”, “method_typ”, “definitiondescription” and “survey_quest_text” revealed that the LOINC domain distribution can be more accurate if used the combinations of LOINC properties. In turn, the Concept Class definition is interconnected with a defined Domain.

So, they were assigned pursuant to the following criteria:

Source Dependencies Domain Concept Class
LOINC Core Table A “classtype” field value = 1 (Laboratory class) or 2 (Clinical class) AND:
1. A “survey_quest_text” field value contains question mark, which always defines LOINC questions.
2. A “scale_typ” field has “Set” value indicating concepts used for Clinical Attachments only.

3. A “property” field value contains:
• “Hx” - History of different clinical and administrative events
• “Anat” - Anatomical sites, points, body structure descriptions
• “ClockTime”, “Date”, “TmStp”, “TmStpRange”, “DateRange” - time/date/date and time/ranges of different clinical and administrative events
• “Desc” - Description of procedures or clinical events
• “Instrct” - Instructions
• “Loc” - Location
• “Pn” - Person Name - administrative information about a person
• “Addr” - Address
• “EmailAddr” - Email Address
• “Tele” - Telephone Number
• “Xad” - also Address
• “Txt” - Text - notes and comments
• “URI” - Uniform Resource Identifier
• “Bib” - Bibliographic Citation
Observation Clinical Observation
4. A “property” field value is “ID” representing Identifiers such as serial numbers, codes and IDS while “system” field value in “BPU” (Blood Product Unit - additional information about a blood transfusion), “^Patient” (patient related codes), “Vaccine” (vaccination-related additional information).

5. Values of a “system” field are represented by the following:
• “^Family member”,“Community”, “^Brother”,“^Daughter”, “^Sister”, “^Son” - observational particular person-related data
• “^CCD” - Continuity of Care Document
• “^Census tract” - information about people in a geographic region defined for the purpose of taking a census
• “^Clinical trial protocol” - Clinical trial protocol documentation and reports
• “*” - Mixed category defining sites, types, locations, device peculiarities, etc.
• “^Contact”, “^Emergency contact” - contact information
• “^Donor” - a donor type and ID
• “^Event” - information about incidents or events
• “^Facility” - information about services
• “Provider” - provider-related information
• “Report” - report specification
• “Repository” - health data repository
• “School” - a name of a school
• “Surgical procedure” - surgical specification
Observation Clinical Observation
6. values of a “system” filed are “^Patient” and “*^Patient” which contain observational data directly linked with a patient and, simultaneously, values of a “scale_typ” field are in:
• “Doc” - various types of documentation
• “Nar” - narrative text
• “Nom” - nominal or categorical responses that do not have a natural ordering
• “Ord” - ordered categorical responses, e.g. “Yes”, “No”.
while a “method_typ” field value is not “Apgar” (Apgar score is a screening test used to measure the vital signs of a newborn)
values of a “property” field are in:
• “Imp” - impression/interpretation of a study - is used to represent a property when the evaluation is a mental abstraction based on one a collection of measurements and/or data.
• “Find” - findings (seem to be Observations in all cases regardless of the “system”, but not)
• “NRat” - number = count/time - e.g. “How many cigars are you smoking per week now?”
• “Num” - number - e.g. “[#] Pregnancies”
• “PrThr” - the presence of symptoms, historical facts, statuses, etc.
• “RelRto” - relative ratio - e.g. relative risk of developing a disease
• “Time” - time aspects - age, hours, years, etc.
• “Type” - a mixed category with a general notion of something
• “Arb” - arbitrary - a mixed category, e.g. “Informed consent obtained” or “RhoGam candidate”
while values of a “class” field are not “COAG” (it includes laboratory, tests related to hemostasis) and “PULM” (it is about measurements of respiratory function).

A general exclusion criterion: a “long_common_name” field value contains the words as “scale” or “score” (they indicate “Measurement” domain).
Observation Clinical Observation
Other cases when a “classtype” field value = 1 (Laboratory class) Measurement Lab Test
Other cases when a “classtype” field value = 2 (Clinical class) Measurement Clinical Observation
A “classtype” field value = 3 (Claims attachment) Observation Claims Attachment
A “classtype” field value = 4 (Surveys) Observation Survey
LOINC Hierarchy A “Code text” field value contains the following:
• “identifier”, “ID”, “number”, “name”, “age”, “status”, “provider”, “subject”, “device”, “version”, “ICD code”, “coding system”, “priority”
• “time”, “date”, “date and time”, “term”
• “comment”, “narrative”, “note”, “directive”, “attachment”, “reference”, “interpretation”, “summary”, “information”, “suggestion”, “administration”, “route”, “instruction”, “intention”, “consent”, “report”, “flowsheet”,
• “recommended”, “reported”, “received”, “requested”, “reviewed”, “ordered”, “available”, “issued”, “performed”,
• “lifetime risk”, “risk factor” “alert”, “known exposure”, “not yet categorized”, “reason for”
At the same time a “code_text” field value does not contain: “thrombin time”, “clotting time”, “bleeding time”, “clot formation”, “kaolin activated time”, “closure time”, “protein feed time”, “Recalcification time”, “reptilase time” ,”russell viper venom time”, “implanted device”,” dosage.vial”, “isolate”, “within lymph node”, “cancer specimen”, “tumor”, “chromosome”, “inversion”, “bioavailable”.
Observation LOINC Hierarchy
Other values of a “code_text” field Measurement LOINC Hierarchy
LOINC Classes LOINC Class name contains such the words as “history”, “report”, “document”, “miscellaneous”, “public health” Observation LOINC Class
Other cases Measurement LOINC Class
LOINC Answer Independently Meas Value Answer


Relationships are defined within LOINC and between LOINC and CPT, and LOINC and SNOMED:

1. Internal LOINC relationships

A purpose of Internal LOINC relationships is to build a LOINC Hierarchy, which makes it easier to sort and browse the database.

Maps toEach LOINC conceptThe same LOINC concept
Is aDescendant LOINC ClassAncestor LOINC Class
Is aLOINC GroupLOINC Group Category
Is aLOINC Measurement or ObservationLOINC Class
Is aLOINC Measurement or ObservationLOINC Group
Is aDescendant LOINC Measurement or ObservationAncestor LOINC Measurement or Observation
Panel containsLOINC PanelLOINC Measurement or Observation
Has AnswerLOINC QuestionLOINC Answer
Has type of serviceLOINC Measurement or ObservationLOINC concept indicating a Type of Service (Document Ontology)
Has subject matterLOINC Measurement or ObservationLOINC concept indicating a Subject Matter Domain (Document Ontology)
Has roleLOINC Measurement or ObservationLOINC concept indicating a Role (Document Ontology)
Has settingLOINC Measurement or ObservationLOINC concept indicating a Setting (Document Ontology)
Has kindLOINC Measurement or ObservationLOINC concept indicating a Kind of Document (Document Ontology)
Concept replaced byUpdated LOINC conceptNew LOINC concept
Reverse RelationshipFromTo
Mapped fromEach LOINC conceptThe same LOINC concept
SubsumesAncestor LOINC ClassDescendant LOINC Class
SubsumesLOINC Group CategoryLOINC Group
SubsumesLOINC ClassLOINC Measurement or Observation
SubsumesLOINC GroupLOINC Measurement or Observation
SubsumesAncestor LOINC Measurement or ObservationDescendant LOINC Measurement or Observation
Contained in panelLOINC Measurement or ObservationLOINC Panel
Answer ofLOINC AnswerLOINC Question
Type of service ofLOINC concept indicating a Type of Service (Document Ontology)LOINC Measurement or Observation
Subject matter ofLOINC concept indicating a Subject Matter Domain (Document Ontology)LOINC Measurement or Observation
Role ofLOINC concepts indicating a Role (Document Ontology)LOINC Measurement or Observation
Setting ofLOINC concepts indicating a Setting (Document Ontology)LOINC Measurement or Observation
Kind ofLOINC concepts indicating Kinds of Document (Document Ontology)LOINC Measurement or Observation
Concept replacesNew LOINC conceptUpdated LOINC concept

2. External LOINC relationships

The purpose of External LOINC relationships is the following: to simplify s cross-analysis of clinical information systems, laboratory information, specifications or standards with a context of combined use of the LOINC and such a coding system as either the SNOMED or CPT4, or PPI.

Relationship From To Description Count
LOINC - SNOMED eq LOINC Lab Test SNOMED concept of 705114005 “LOINC Code System” (Qualifier Value) An identifier for a LOINC referenced component according to the "Using LOINC with SNOMED CT" guide. Note, this is not a mapping! 22560
LOINC - SNOMED eq LOINC Hierarchy SNOMED Body Structure (the “Spec Anatomic Site” domain) Defines a body structure observed or measured 26
LOINC - SNOMED eq LOINC Hierarchy SNOMED Morph Abnormality (the “Observation” domain) Indicates present in certain disease states structures which observed or measured 3
LOINC - SNOMED eq LOINC Hierarchy SNOMED Observable Entity (the “Observation” domain) Represents an entity observed or measured 8
LOINC - SNOMED eq LOINC Hierarchy SNOMED Organism (the “Observation” domain) Defines a microorganism measured 116
LOINC - SNOMED eq LOINC Hierarchy SNOMED Substance (domains of “Device” and “Observation”) Represents a biological substance or pharmacological agent measured 849
LOINC - SNOMED eq LOINC Hierarchy SNOMED Specimen (the “Specimen” domain) Indicates a specimen source observed or measured 4
LOINC - CPT4 eq LOINC Lab Test CPT4 Procedure or Measurement Defines link from a LOINC concept to a less granular CPT4 concept 1886
Mapped from LOINC Survey/Clinical Observation/Answer PPI Observation or Measurement Indicates an equivalent mapping from a concept of the PPI questionnaire-like vocabulary to a corresponding LOINC concept 2155


All internal “Is a” and “Panel contains” relationships participate in the creation of the CONCEPT_ANCESTOR table, creating an internal hierarchy within the LOINC. Note, the LOINC hierarchy is not connected to the SNOMED hierarchy which is the core Domain space for Measurement and Observation in OHDSI vocabularies.

documentation/vocabulary/loinc.txt · Last modified: 2019/05/24 11:00 by ptalapova