[Quality assurance or quality control. Lessons from an intercomparison circuit]

This article deals with the evaluation of the three year results of the French interlaboratory control for serum copper and zinc analysis. We pointed out some results interpreted on the basis of the existence of differences between the notions of quality control and total quality assurance. The main finding was a surprising change in the annual range in the final results of the laboratories. All 'good' laboratories in the first year showed a significant fall in their individual performance the second year. We can interpret that as a falling off of vigilance in relation with the self satisfaction after the publication of the first results. We concluded that good laboratory practices must be accompanied by a quality program not limited to an analytical control.