Scales for Measurement Based on an Antigen-Antibody Reaction

Abstract

In spite of sometimes complicated reaction sequences, the multitude of immunomethods all rely on the principle of a reaction between an antigen and an antibody and follows physico-chemical kinetics according to molecular relationships. The preferred kind-of-quan-tities for amount of analyte, therefore, should be number of entities (unit: 1) and amount-of-substance (mol) - both requiring definition of the elementary entity of the analyte - rather than mass (kg) and arbitrary amount-of-substance(procedure) (arbitrary unit). Derived kind-of-quantities for concentration (dividing by volume of system) and content (dividing by mass of system) are easily defined. The measurement scale is an ordered set of possible values that the quantity may take. Any scale should be described as to type and the magnitudes and number of possible values. The types comprise nominal (no magnitudes), ordinal (inequality of magnitudes), difference (equality of differences), and ratio scales (equality of ratios). Each scale is characterized by the statistics allowed with the measured values. The magnitudes of possible values are derived from the nature of the quantities being considered and the measurement procedure. The number of possible values will vary from two to many and depends on the uncertainty of results delivered by the procedure. With this systematic description, the ambiguous terms “qualitative” and “semiquantitative” may be abandoned. A given analyte in a certain type of system may give rise to values on any of the scales if it can be measured on a ratio scale because simpler and chemically less informative results may be obtained by transformation.