Pre- and postanalytical errors in haematology.

The majority of errors in laboratory medicine occur in the pre- and postanalytical phases of the testing process. Although the causes of these errors are largely common to all laboratory medicine specialties, it is important for the haematology laboratory to understand the particular impact of some on automated counting. The preanalytical phase is the stage of greatest risk but preanalytical errors may go undetected until postanalytical validation and interpretation. The challenges in the postanalytical phase include the standardisation of reference intervals against which results can be interpreted and the impact of just a small difference in reference interval for a key analyte such as haemoglobin concentration. Quality indicators against which pre- and postanalytical error incidence are measured are a source of information that can be used to improve services but laboratories struggle to collect good quality data.