SNOMED Documentation Search
This section contains a high-level overview of LOINC with some additional information
in areas of direct relevance to subsequent chapters of this guide. For a more complete
introduction to LOINC and supporting resources see http://loinc.org/get-started.
Logical Observation Identifiers Names and Codes (LOINC®) is a terminology standard for identifying laboratory tests and other measurements.
It specifies universal codes, names, and other attributes for laboratory results as
well as clinical reports, physical exam findings, survey instruments and other observations.
It was developed to enable the exchange and pooling of results from diverse sources
in order to enhance clinical care, outcomes management and research.
LOINC codes include laboratory and other clinical observations. The laboratory portion
of LOINC includes measurements made on specimens, such in chemistry, hematology, serology,
microbiology (including parasitology and virology), toxicology, cell counts, antibiotic
susceptibilities, and more. The clinical portion of LOINC includes codes for observations
made on patients and populations. LOINC has codes for observations like vital signs
and a wide range of other clinical observations. Vital signs and anthropomorphic measurement
are included in the scope of the cooperation agreement. Other clinical domains are
not currently included in the scope of the agreement with IHTSDO.
LOINC includes codes that identify test observations (e.g. blood culture, antibiotic
sensitivity). Other code systems, including SNOMED CT, often provide values that can be applied
to represent results (e.g. staphylococcus, amoxicillin). If we consider the observation
as a question and the observation values as answers, LOINC provides codes for the
questions and SNOMED CT provides codes for many of the non-numeric answers.
LOINC is owned, maintained and licensed by the Regenstrief Institute, Inc. (RII). RII is a non-profit medical research organization associated with Indiana University School of Medicine. LOINC is available free of charge subject to the license conditions and terms of use . Updated versions are released twice a year. The LOINC web search tool is available at . The LOINC database and a free browsing and mapping program, the Regenstrief LOINC Mapping Assistant (RELMA®), can be downloaded from .
LOINC is widely adopted, and the user community continues to grow rapidly. The worldwide
LOINC community presently has more than 34,000 users in 163 countries (see http://loinc.org/atlas).
Within the USA, LOINC has been adopted by large reference laboratories, health information
exchanges, healthcare organizations, insurance companies, research applications, and
several national standards initiatives and programs. In particular, LOINC was adopted
as the standard for laboratory orders and results as part of the Centers for Medicare
and Medicaid Services Electronic Health Record (EHR) "Meaningful Use" incentive program
as specified in the Standards and Certification Criteria.
Outside the USA, LOINC has also been adopted as a national standard in more than 25
countries. In addition, there are many large data exchanges using LOINC around the
world.
Each test is represented by a formal six-part LOINC name and assigned a LOINC code,
which is a number with a check digit (see Table 1). Each code is also assigned an
observation class (e.g., chemistry, hematology, and radiology); related names (to
assist searches of the database); and other attributes.
For most classes of laboratory observations, there is also a "short name" (less than
40 characters long), and a Long Common Name that is more clinician friendly.
LOINC fully-specified names (including laboratory test results, clinical measurements,
and results of other diagnostic studies) are defined in terms of six major axes as
described in Table 2: 1. Component name, 2. Property, 3. Time, 4. System, 5. Scale,
and 6. Method. The fully-specified (formal) LOINC name must include entries for the
first five major axes; the method axis is included only when the method distinction
makes an important difference to the clinical interpretation of the result.
Four additional minor axes are challenge information; adjustments; supersystem, e.g.,
fetus, blood product; and time operators (maximum, minimum, last, first), which are
only used when relevant. The challenge axis is the most complex of the minor axes
and includes the amount, route, and timing (e.g., oral glucose tolerance test). The
details about these other axes can be found in the LOINC Users 'Guide.
Examples of LOINC terms are shown in Table 1.
Table 1.Examples of laboratory LOINC codes and formal LOINC names.
LOINC Code |
LOINC name (Componentname:Property:Time:Specimen:Scale:Method) |
|
|
2951-2 |
SODIUM:SCNC:PT:SER/PLAS:QN |
2955-3 |
SODIUM:SCNC:PT:UR:QN |
2956-1 |
SODIUM:SRAT:24H:UR:QN |
2164-2 |
CREATININE RENAL CLEARANCE:VRAT:24H:UR:QN |
1514-9 |
GLUCOSEˆ2H POST 100 G GLUCOSE PO:MCNC:PT:SER/PLAS:QN |
3665-7 |
GENTAMICINˆTROUGH:MCNC:PT:SER/PLAS:QN |
17863-2 |
CALCIUM.IONIZED:MCNC:PT:SER/PLAS:QN |
2863-9 |
ALBUMIN:MCNC:PT:SNV:QN:ELECTROPHORESIS |
(http://www.clinchem.org/content/49/4/624.full.pdf)
Table 2.Formal model for constructing LOINC fully specified names
Axis Name |
Description/Example |
|
|
Component name |
The analyte or attribute being measured or observed. E.g., sodium, body weight. |
(Kind of) Property |
Differentiates kinds of quantities relating to the same substance. E.g., mass concentration, catalytic activity. |
Time (Aspect) |
Identifies whether the measurement is made at a point in time or a time interval. E.g. 24H for a urine sodium concentration. |
System |
The specimen, body system, patient, or other object of the observation. E.g. cerebral spinal fluid, urine, radial artery. |
(Type of) Scale |
The scale or precision that differentiates among observations that are quantitative, ordinal (ranked choices), nominal (unranked choices), or narrative text. |
(Type of) Method |
An optional axis that identifies the way the observation was produced. It is used only when needed to distinguish observations that have clinically significant differences in interpretation if made by different methods. |
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3376691/pdf/nihms355669.pdf)
LOINC creates only those combinations that have clinical relevance in laboratory medicine.
Terms are not created by blind permutations. Regenstrief (with guidance from the LOINC
committee) reviews new code requests carefully to make sure that only meaningful LOINC
codes that can be pragmatically used by the LOINC community are added to the database.
The atomic elements that comprise a fully-specified LOINC name are called LOINC "Parts".
Each fully-specified name will consist of 5 or 6 parts (depending on whether the Method
is important for interpreting the result), each with a part type corresponding to
one of the major axes described above. Each LOINC Part is also assigned an identifier
(that begins with the prefix "LP"), and internally Regenstrief maintains links between
the full LOINC term and the Parts that comprise it. Regenstrief uses LOINC Parts in
many aspects of LOINC development, such as: adding synonymy, building hierarchies,
creating alternate display names, linking descriptive text, and more.
The Parts and their linkages are not distributed as part of the main LOINC table,
but they are part of the content used by the RELMA program.
LOINC "part" concepts (e.g. sodium) serve as building blocks for the description of tests and observations, in association
with a set of semantic relations. For example, Sodium:SCnc:Pt:Ser/Plas:Qn, the laboratory test in which the molar concentration of sodium is measured in the
plasma (or serum) is identified by 2951-2. The list of relations of this concept to
other concepts ("parts") is shown in Table 3 and Table 4. For example, the "part"
concept Sodium is linked to this test by the relationship component.
Table 3.Example of the relation of the LOINC code 2951-2 to LOINC Part codes
|
LOINCCode |
LOINC Name |
LOINCTerm |
2951-2 |
Sodium [Mass or Moles/volume] in Serum or Plasma |
Part Type |
Part No. |
Part Name |
Component |
LP15099-2 |
Sodium |
Property |
LP6860-3 |
SCnc [Substance Concentration] |
Time |
LP6960-1 |
Pt [Point in time (spot)] |
System |
LP7576-4 |
Ser/P1as [Serum or Plasma] |
Scale |
LP7753-9 |
Qn |
Method |
|
|
(http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2655945/)
Table 4Example of the relation of the LOINC code 5778-6 to LOINC Part codes
|
LOINCCode |
LOINC Name |
LOINC Term |
5778-6 |
Color of Urine |
Part Type |
Part No. |
Part Name |
Component |
LP28806-5 |
Color |
Property |
LP6886-8 |
Type |
Time |
LP6960-1 |
Pt [Point in time (spot)] |
System |
LP7681-2 |
Urine |
Scale |
LP7750-5 |
Nom [Nominal] |
Method |
|
|
The LOINC terminology does not use description logic. However, the formal definitions
provided by LOINC all conform to the 6-axis template (described in Table 2) and make
use of named semantic relations.
In addition to creating codes for single tests, measurements, or observations, LOINC
also defines concepts to represent collections of discrete elements such as panels
(batteries), forms, and data sets.
For example, a CBC/FBC test (complete/full blood count) is expected to deliver a set
of results for different components including leukocytes, erythrocytes, hemoglobin,
hematocrit, etc.
Regenstrief creates hierarchies to organize LOINC terms based on a structured arrangement of LOINC elements (also known as parts).RELMA has 5 selectable hierarchy trees that are commonly used to narrow the search limits returned:
The LOINC hierarchy group LOINC concepts by specifying the parent-child relationship
between the elements used in one (or more of the axes).
Most often, the hierarchies are used to restrict searches performed using RELMA.
The Multiaxial hierarchy organizes LOINC codes based on more than one of the LOINC
name axes. For laboratory tests, it organizes first by the Component and then by the
System. The Multiaxial Hierarchy is distributed as an accessory file that is part
of the LOINC release.
Figure 1.Class hierarchy showing Class classification of laboratory tests
Figure 2.Multiaxial hierarchy of LOINC showing relations in Microbiology parts of component
Figure 3.Multiaxial hierarchy of LOINC showing relations in system ax: specimen
McDonald CJ, Huff SM, Suico JG, Hill G, Leavelle D, Aller R, Forrey A, Mercer K, DeMoor
G, Hook J, Williams W, Case J, Maloney P. LOINC, a universal standard for identifying
laboratory observations: a 5-year update. Clin Chem. 2003 Apr;49(4):624-33. http://www.clinchem.org/content/49/4/624.full.pdf+
Vreeman DJ, Chiaravalloti MT, Hook J, McDonald CJ. Enabling international adoption
of LOINC through translation. J Biomed Inform. 2012 Aug;45(4):667-73.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3376691/pdf/nihms355669.pdf+
Bodenreider O. Issues in mapping LOINC laboratory tests to SNOMED CT. AMIA Annu Symp
Proc. 2008 Nov 6:51-5.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2655945/pdf/amia-0051-s2008.pdf+
Steindel S, Loonsk JW, Sim A, Doyle TJ, Chapman RS, Groseclose SL. Introduction of
a hierarchy to LOINC to facilitate public health reporting. Proc AMIA Symp. 2002:737-41.
Adamusiak T, Bodenreider O. Quality assurance in LOINC using Description Logic. AMIA
Annu Symp Proc. 2012;2012:1099-108.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3540427/pdf/amia_2012_symp_1099.pdf+