The acronym stands for “Logical Observation Identifiers Names and Codes.” In the early 1990s, several US labs combined eachof their sets of codes into a list of all possible clinical laboratory tests. A LOINC (Logical Observation Identifiers Names and Codes©) number was then assigned to each test. Like CPT, the codes were originally developed in order to bill for the test, not to convey information about the purpose or result of the test.
Public Health Agencies and the government use the system because LOINC uses a highly structured system for naming laboratory tests, in which each test name consists of six pieces of information. They are:
Component – The analyte or that which is tested. Examples: Cefoperazone, Norwalk virus, Plasmodium falciparum Ag, Lead, etc. Property – The property of the Component that is measured. Examples: Susceptibility, Presence or Identity, Mass concentration, Arbitrary concentration, etc. Time aspect – The duration of the test period. Examples: Usually “Point in time” but can be 1 hr, 12 hrs, 24 hrs, etc. System – The specimen type Examples: Isolate, Stool, Serum or Plasma, Blood, etc. Scale type – This determines how the test result is expressed and the type of units used. Examples: Quantitative, Nominal, Ordinal (Positive, Negative, Intermediate, etc.)Method type – The method used in the test procedure. Examples: Agar diffusion, Electron microscopy, Immunofluorescence, etc.
The table below shows some LOINC codes and names.
| LOINC Num | LOINC Name |
| 101-6 | Cefoperazone : Susc : Pt : Islt : OrdQn : Agar diffusion |
| 10696-3 | Norwalk virus : PrId : Pt : Stl : Nom : Microscopy.Electron |
| 10912-4 | Lead : MCnc : Pt : Ser/Plas : Qn : |
| 10709-4 | Plasmodium falciparum Ag : ACnc : Pt : Bld : Qn : IF |
