Preanalytical factors and their influence on analytical quality specifications.

Whereas analytical standards are described by established quality control criteria, no such standards exist for defining the quality of the preanalytical phase. A working group of the German Society for Clinical Chemistry and Laboratory Medicine has defined recommendations to describe the quality criteria for materials and processes used in the diagnostic process between patients and the analytical step. Thus, the quality of the sample may be defined regarding its adequacy and amount, as well as anticoagulants and stabilizers used. Timing of sampling, transport and storage involve criteria on sample stability, proper transport and preanalytical treatment. Moreover, sample identification, storage, and handling of interference and influence factors can be documented in quality manuals for the preanalytical phase. These possible variables have been discussed in five European expert meetings and recommendations published in national journals and presented in book form.