The Italian external quality assessment scheme for trace element analysis in body fluids.

We describe the operative procedures of the Italian external quality assessment scheme (EQAS) for the determination of trace elements in body fluids. The aims of the scheme are both the education of participants and the continuous development and optimization of procedures for collaborative EQA trials. Participation is free of charge. Interlaboratory exercises for EQA are organised every three or four months for the determination of cadmium and lead in blood; aluminium, copper, selenium and zinc in serum; chromium and nickel in urine. Freeze-dried control materials are prepared in the laboratory from animal blood or human urine. In each trial, each participant receives from six to eight samples, chosen from among the pools selected for that occasion using a randomised strategy and including unknown duplicate specimens. Laboratory performances are evaluated on the basis of proximity to target values, differences in results for duplicate samples and comparison with established acceptability limits. The development of dedicated software for the bidirectional transmission of data between the organising centre and the peripheral laboratory gives the participants the chance to verify immediately the quality of their results and take action without delay, if needed.