total allowable error (TEa)

Total allowable error is a selected limit for the combined analytical error considered acceptable for a particular examination and intended use. It may be expressed as a percentage, an absolute concentration difference, or a combination that changes with concentration. The source can be a clinical requirement, a regulatory criterion, or another justified analytical performance specification; these sources need not produce identical limits.

TEa is a performance goal, not an observed error and not a measurement-uncertainty estimate. Record which specification is being used and why it is appropriate for the patient population and decision points. When applying it to verification, quality-control planning, or sigma calculations, ensure that units, concentration ranges, and the treatment of bias and imprecision are consistent with the intended calculation.

For accreditation, explicit performance goals make acceptance decisions transparent and reproducible. A laboratory should be able to explain why its selected allowance supports clinical use rather than simply choosing the easiest target to meet. Review the goal when intended use changes, and investigate methods that cannot reliably achieve the required performance at important decision concentrations.