Logical Observation Identifier Names and Codes (LOINC)
LOINC is a consortium of laboratories, system vendors, hospitals, and academic institutions organized by the Regenstrief Institute and supported by grants from the John A. Hartford Foundation of New York, the Agency for Health Care Policy and Research, and the National Library of Medicine.
LOINC is a consortium, not a formal SDO. However, it is designed to work in conjunction with the HL7/ASTM and CEN observation (result) messages.
Logical Observation Identifiers Names and Codes (LOINC).
Contact For More Information
Stan Huff <firstname.lastname@example.org>
36 South State St, Suite 800
Salt Lake City, UT 84111
Phone: 801 442 4885
Fax: 801 263 3657
Clem McDonald <email@example.com>
Indiana University School of Medicine
1001 W. 10th St. 5th fl RHC
Indianapolis, IN 46202
Phone: 317 630 7070
Fax: 317 630 6962
To obtain the Users' Guide, and full LOINC database in report, ASCII text, or dBase formats:
(1) Laboratory LOINC
LOINC concentrates on the identification and naming of test and clinical observations, things like diastolic blood pressure, serum glucose, blood culture, or "heart physical exam." LOINC does not deal formally with the values reported for these observations/measurements, some of which are valued as numbers, and some of which are valued as codes or text. Most of these coded answers are expected to be provided from other sources, such as SnoMed, CPT4, ICD9CM, and other code systems.
The laboratory component of the data base is fairly complete with respect to the tests listed in Table 1.
Table 1 Subject matter covered by Lab LOINC
Microbiology including cultures, microscopic examinations, RNA and DNA probes,
Antibody and antigen measures
Antimicrobial susceptibility testing
Toxicology and drug testing
Blood counts and Urinalysis
Each record in the LOINC data base identifies one distinct observation. Each record contains the LOINC identifier, which is a meaningless number with a self check digit, and a multi-part formal name which includes component (e.g., glucose, intra-arterial diastolic), type of property (e.g., mass concentration, pressure), timing (e.g., point measure 24 hour), system (e.g., serum, brachial artery), scale (e.g., quantitative, qualitative), and method (e.g., dip stick, ausculatory).
In addition, the data base contains related names (near synonyms), molecular weights, indicators of terms that have been retired, a pointer to the terms that replace them, and related codes from other systems, e.g., the chemical abstract code for chemical substances.
With the data base comes a manual that provides formal rules for naming the parts of an observation, and a full definition of the data base.
LOINC does not yet include names for order sets, e.g., CHEM12.
Figure 1 Example Laboratory LOINC codes
1919-0 ASPARTATE AMINOTRANSFERASE:CCNC:PT:FLU:QN
4531-0 COMPLEMENT TOTAL HEMOLYTIC:PT:BLD:QN
9782-4 ADENOVIRUS SP IDENTIFIED:PRID:PT:XXX:QL:ORGANISM SPECIFIC CULTURE
4991-6 BORRELIA BURGDORFERI DNA:ACNC:PT:XXX:SQ:AMP/PROBE
6324-8 BRUCELLA ABORTUS AB:TITR:PT:SER:QN:AGGL
6337-0 CANDIDA ALBICANS AG:ACNC:PT:SER:SQ:ID
9822-8 MICROORGANISM IDENTIFIED PRID:PT:DIAF:QL:STERILE BODY FLUID CULTURE
6981-5 AZITHROMYCIN:SUSC:PT:ISLT:SQN:GRADIENT STRIP
6473-3 MICROSCOPIC OBSERVATION:PRID:PT:TISS:QL:TRICHROME STAIN
The same general approach has been applied to common clinical measures as to laboratory observations. The same six major parts of the name, some with subparts, are used.
Table 2 Subjects covered in clinical LOINC
Blood pressure (systolic, diastolic, and mean)
Heart rate (and character of the pulse wave)
Critical care measures
(Cardiac output, resistance, stroke work, ejection fraction, etc.)
Body Weight (and measures used to estimate ideal body weight)
Circumference of chest, thighs, legs, etc.
Intake and output
Major headings of history and physical
Major headings of discharge summary
Major headings of an operative note
Clinical LOINC code numbers are taken from the same sequence of numbers as the Lab LOINC codes.
For many clinical measures, measurements are distinguished for estimated, reported, and measured values. (E.g., a patient's report of his or her body weight is a different variable from a measured result or the physician's estimate.) Also varying degrees of pre-coordination are provided for the observation, the body site at which it was obtained, and the method. E.g., a cardiac output based on the Fick method is distinguished from a cardiac output based on a 2D cardiac echo.
Physiologic measures are often monitored continuously over time, and the instrument reports summary "statistics" over that reporting period. The summary statistics can include minimum, maximum, and mean over a time period for vital signs measurements and fluid intake and output. When we address measures taken over time, we usually include 1 hour, 8 hour, 10 hour, 12 hour, and 24 hour summaries. The middle three durations are included to cover the varying durations of work shifts within and across institutions.
The parts of clinical measurement names are the same as for laboratory measures. The fourth part, the system, usually identifies an organ system or a particular part of the anatomy. For a measure of systolic left ventricular pressure, the system would be "Cardiac ventricle.left." In contrast to laboratory tests, where the component is usually some chemical entity, the clinical measurement component usually identifies the specific aspect of a property that is measured. For example, the property type might be pressure. Then the component would identify the pressure measured as intravascular diastolic. In general the component is used to distinguish the various points or ranges, or inflections of a physiologic tracing, and to define precisely which of a number of possible dimensions of length or area are being measured in imaging.
Laboratory measures tend to be more regular than clinical measures. The system is usually a specimen and the component a chemical or molecular moiety. For most clinical measurements, the component is also an attribute of a patient or an organ system within a patient. However, attributes of non-patient entities are often of interest in the case of clinical measurements. For example, we might want to know the class of instrument used to obtain the measurement.
Figure 2 Example Clinical LOINC terms
8285-5 CIRCUMFERENCE.OCCIPITAL-FRONTAL:LEN:PT:HEAD:QN:TAPE MEASURE
8496-2 INTRAVASCULAR DIASTOLIC:PRES:PT:BRACHIAL ARTERY:QN
9940-8 Q WAVE DURATION:TIME:PT:LEAD V1:QN:EKG
8660-3 HISTORY OF SYMPTOMS & DISEASES:FIND:PT:CARDIOVASCULAR SYSTEM:QL:REPORTED
8651-2 HOSPITAL DISCHARGE DX:IMP:PT:^PATIENT:QL
9129-8 FLUID OUTPUT.CHEST TUBE:VOL:PT:PLEURAL SPACE:QN
The LOINC database of over 10,000 observations/measurement/test result codes is available for free use on the Internet.
There is only one official version of the LOINC standard. Codes are never re-used when the meaning of a term changes. Updates and additions are made at two to three month intervals.
Indicators Of Market Acceptance
The laboratory component of LOINC was installed on the Internet in April of 1995, and has been greeted enthusiastically since. It has been endorsed by the American Clinical Laboratory Association (ACLA) and recommended for adoption by its members. The ACLA is the association of large referral laboratories, and its members are responsible for more than 60% of US outpatient laboratory volume. Corning MetPath and LabCorp, two of the largest commercial laboratories, have adopted LOINC as their code system for reportable test results, as has LifeChem and Associated Regional and University Pathologists (ARUP). In addition, Indiana University labs, University of Colorado, Intermountain Health Care, University of Missouri, and Barnes/Jewish Hospital are in the process of converting their reporting to LOINC codes. The province of Ontario, Canada has made a tentative commitment to the LOINC codes for a province-wide coding standard.
The LOINC codes have been used as the basis for HCFA's ICD10-PCS laboratory codes. They have been incorporated in HCFA's quality assurance testing pilot software, and they have been adopted by the Centers for Disease Control and Prevention/State and Territorial Epidemiologist project for transmitting communicable diseases reports electronically.
Level of Specificity
The identifiers are specific in up to eight dimensions. The goal is to match the level of specificity provided by the master files of the systems that report these kinds of results. Laboratory test results are distinguished (and specific) to the analyte (e.g., glucose), the type of property (e.g., mass concentration), the timing aspects (e.g., 24 hour specimen), the specimen, (e.g., urine), and the method - as needed. In the case of serology tests, which tend to include method information in their name, LOINC includes the methods. In the case of chemistry tests, that tend not to include method information in their name, the LOINC codes tend not to be specific about method. The data base now includes over 10,000 laboratory and clinical observations.
The LOINC data base and Users' Guide is available for free use for any purpose by users and vendors from the Internet Web site listed above. It is copywritten in order to prevent the development of multiple variants.