Experiences with a regional quality control scheme for salicylate and paracetamol over a period of two years.

The organisation of a regional quality control scheme for salicylate and paracetamol estimations in plasma is described. The results show considerable variation in both bias and precision between laboratories, with some overall improvement in performance during the second year of the scheme. No method can be singled out as producing better results than the others. The major factor seems to be the care with which the analyses are performed.