HL7^® Reference Guide

HL7-defined table of codes that describe the underlying kind of property represented by an observation. The categories distinguish concentrations from total amounts, molar concentrations from mass concentrations, partial pressures from colors, and so forth. These are discussed more fully in the LOINC Users' Manual. They are derived from the approach described in 1995 edition of the IUPAC Silver Book. These distinctions are used in IUPAC and LOINC standard codes. The distinctions of true quantities in this table are based primarily on dimensional analyses. The table contains a number of "families," those related to simple counts (number, number concentration, etc.), to mass (mass, mass concentration, etc.), to enzyme activity (catalytic content, catalytic concentration, etc.), and molar or equivalents (substance content, substance concentration).