How is linearity defined in laboratory measurements?

Linearity in laboratory measurements refers to the ability of an analytical method to give results that are directly proportional to the concentration of the analyte in a sample across a specified range. When a measurement is linear, it means that as the concentration of the analyte increases or decreases, the measured output also changes in a consistent manner. This relationship is crucial for ensuring accuracy and reliability in quantitative laboratory tests, allowing for clear and predictable interpretations of results over the range of concentrations that the assay is designed to measure.

The definition emphasizes that for a given analytical result, the relationship must remain proportional, which is foundational in standard curve construction and calibration in analytical chemistry. Establishing linearity is essential for quantifying unknown samples since it assures that calculations and concentrations derived from the data are valid within that tested range.

While consistency of repeated measurements, proximity to true value, and variability between different methods are important concepts in quality control and validation of assay performance, they do not specifically define linearity as it pertains to how the results relate to analyte concentration.