A Model for an Uncertainty Budget for Preanalytical Variables in Clinical Chemistry Analyses

Background: We sought a practical method to calculate preanalytical uncertainties. In clinical chemistry mea-surements, the combined preanalytical uncertainty is a function of the magnitude and probability distribution of the different uncertainty sources and the number of such sources. Methods: Results from an optimal practice for handling of the blood samples (termed the standard method) were compared with alternative methods that deviate from the standard method but are used in current practice. For categorically distributed uncertainty sources (e.g., use of different kinds of blood tubes), alternative treatments were modeled discretely using a known probability dis-tribution for each alternative. For continuously distributed sources (e.g., clotting time), we assumed a rectangula