Comparison of some European external quality assessment schemes in the field of occupational and environmental medicine.

In most European countries an increasing number of external quality assessment schemes (EQAS) are organized, and it seems appropriate to reinforce collaboration at the European level between organizers of EQAS related to occupational and environmental medicine. Since differences between these EQAS have been recognized, a collaborative project was set up focused on the ways the present occupational and environmental medicine EQAS evaluate results obtained by the same pool of laboratories analysing identical control samples for blood lead. The results confirmed that the samples delivered to the laboratories were homogeneous. Considering the performance as judged by five different schemes the study revealed that laboratories were not ranked identically. For laboratories, which either had a very bad or a very good performance, however, the ranking were comparable. The statistical design of the evaluated EQAS poses problems and requires attention.