engleski

Preanalytical variation and preexamination processes

The preanalytical phase has long been recognized as a source of substantial variability in laboratory medicine. Laboratory errors, mostly due to some defect in the preanalytical phase, may lead to diagnostic errors. Understanding preanalytical variation and reducing errors in the pre-examination phase of the testing process are therefore important for improved safety and quality of laboratory services delivered to patients. There are numerous preanalytical factors which may affect the concentration of the analyte, the measurement procedure, or the test result. These factors may be divided into two major groups: influencing and interference factors. Influencing factors are effects on laboratory results of biological origin which most commonly occur in vivo, but can also be derived from the sample in vitro during transport and storage. Biological influence factors lead to changes in the quantity of the analyte in a method independent way. Interference factors (interferences) are defined as mechanisms and factors which lead to falsely increased or decreased results of laboratory tests of a defined analyte. Interference factors and their mechanisms differ with resepct to the intended analyte and analytical method. Interference factors do not affect the concenteration of the analyte. On contrary, they alter the test result for a specific analyte, after the sample has been collected. They are different from the measured analyte and interfere with the analytical procedure. Therefore their effect is method dependent and may thus be reduced or eliminated by selecting a more specific method. This chapter describes the most common preanalytical sources of variability (influences and interferences) and provides recommendations on how to deal with them in everyday practice.

preanalytical phase, quality, hemolysis, interference

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