Logical Observation Identifiers Names and Codes (LOINC)

Laboratory tests and observations are coded using the LOINC coding system. Written and maintained by the Regenstrief Institute, there are over 70,000 codes, each of which is a six-digit number, the last number being separated by the other numbers with a hyphen. Like CPT codes, a specific type of laboratory test (or example, white blood cell (WBC) count) often has multiple codes that vary, depending on the timing of the sample, the measurement units, the measurement method, and so on. While each code contains a large amount of information, this may pose a problem when trying to find a code for a lab test such as a WBC count when not all of the relevant information is known.