This article describes practical problems in carrying out witness audits in terms of the international normal ISO 15189, with special regard to the situation in medical diagnostic laboratories in Germany. The presence of central laboratories – for example in hospitals – and decentralised laboratories – usually in the private sector – present different problems, especially in terms of the preanalytical phase and its control during witness audits for laboratories accredited according to ISO 15189.
Whereas the preanalytical phase can be – at least in theory – controlled completely in and by a centralised hos- pital laboratory, for example by the use of “sample-collection teams”, the problems in preparation and transporting of samples from a peripheral practice to a decentralised analytical laboratory cannot be fully controlled. Other aspects of the preanalytical phase including biological variability, wrong specimen additives, wrong patient preparation and the ADR 2005 / UN Packaging regulations are briefly discussed together with the aims of an optimised pre-analytical phase.
The paragraphs of the normal ISO 15189 which cannot be fully controlled during a witness audit are listed, together with compromise solutions.
DOI: Clin. Lab. 2005;51:665-671