A LOINC term is defined as the combination of the LOINC code and the Fully-Specified Name (FSN).

The LOINC code is a unique, permanent identifier. The LOINC code has no intrinsic structure except that the last character in the code is a mod 10-check digit. The algorithm to calculate this check digit is given in Appendix C. All of the structure associated with a single LOINC entity is stored in other fields in the LOINC database.

The FSN is composed of five or six main Parts: the name of the Component or Analyte measured (e.g., glucose, propranolol), the Property observed (e.g., substance concentration, mass, volume), the Time Aspect of the measurement (e.g., is it over time or momentary), the type of System or sample (e.g., urine, serum), the Scale of measurement (e.g., qualitative vs. quantitative), and where relevant, the Method of the measurement (e.g., radioimmunoassay, immune blot).

The FSN is the combination of the main Parts and the colon character, “:”, which acts as a separator:

<Analyte/component>:<kind of property of observation or measurement>:<time aspect>:<system (sample)>:<scale>:<method>

Note Each attribute of the LOINC Fully Specified Name other than the Method should be valued for every active LOINC term. In some cases, such as for panel terms, one or more attribute values may be a dash (–), but none of the primary attributes should have null values other than the Method.

The first part of the name can be further divided up into three subparts, separated by carats (^). The first subpart can contain multiple levels of increasing taxonomic specification, separated by dots (.). The third and fourth parts of the name (Time Aspect and System) can also be modified by a second subpart, separated from the first by a carat. In the case of Time Aspect, the modifier can indicate that the observation is one selected on the basis of the named criterion (maximum, minimum, mean, etc.); in the case of System, the modifier identifies the origin of the specimen if not the patient (e.g., blood donor, fetus, and blood product unit). The hierarchical structure is outlined in Table 1, with references to the section numbers where each item is explained in detail.

Table 1: Hierarchical Structure of Fully Specified Analyte Name

Subpart NameSection
Component/Analyte2.2
Name and modifier2.2.1
Component/Analyte name2.2.1.1
Component/Analyte subname2.2.1.2
Information about the Challenge (e.g., 1H post 100 gm PO challenge)2.2.2
Adjustments/corrections2.2.3
Kind of Property (mass concentration, mass)2.3
Time Aspect (point or moment in time vs. time interval)2.4
System/sample type (urine, serum)2.5
“Super System” (patient, donor, blood product unit)2.5.2
Type of Scale (nominal, ordinal, quantitative)2.6
Method type2.7

We used Tietz15, Henry16, IUPAC17, EUCLIDES18, diagnostic microbiology textbooks, such as Mahon and Manuselis19, the American Association of Blood Banking20, and other sources as well as the expertise of the individuals or the committee to choose preferred names.

Here are some examples of fully specified LOINC names:

Sodium:SCnc:Pt:Ser/Plas:Qn:
Sodium:SCnc:Pt:Urine:Qn:
Sodium:SRat:24H:Urine:Qn:
Creatinine renal clearance:VRat:24H:Ur+Ser/Plas:Qn:
Glucose^2H post 100 g glucose PO:MCnc:Pt:Ser/Plas:Qn:
Gentamicin^trough:MCnc:Pt:Ser/Plas:Qn:
ABO group:Type:Pt:Bld^donor:Nom:
Body temperature:Temp:8H^max:XXX:Qn:
Chief complaint:Find:Pt:^Patient:Nar:Reported
Physical findings:Find:Pt:Abdomen:Nar:Observed
Binocular distance:Len:Pt:Head^fetus:Qn:US.measured

  1. Burtis CA, Ashwood ER, Burns DE (editors). Tietz Textbook of Clinical Chemistry, 5th ed. Philadelphia: W.B. Saunders; 2013. ↩

  2. Henry JB. Clinical Diagnosis and Management by Laboratory Methods. Philadelphia:W.B. Saunders; 1994. ↩

  3. International Union of Pure and Applied Chemistry/International Federation of Clinical Chemistry. The Silver Book: Compendium of terminology and nomenclature of properties in clinical laboratory sciences. Oxford: Blackwell Scientific Publishers; 1995. ↩

  4. Euclides Foundation International. EUCLIDES Laboratory Investigation Codes. Available from Dr. Georges DeMoor, Euclides Foundation International nv, Excelsioriaan 4A, B-1930, Zaventern, Belgium. Phone: 32 2 720 90 60. ↩

  5. Mahon CR, Manuselis G (editors). Textbook of Diagnostic Microbiology. Philadelphia:W.B. Saunders; 1995. ↩

  6. Walker RH. American Association of Blood Banks Technical Manual. 11th ed. Bethesda, MD: Amer Assoc of Blood Banks, 1993. ↩

Section Contents