title: The importance of internal quality control data in National External Quality Assessment schemes. Plasma progesterone assays.
abstract: Co-ordinators of external quality assessment schemes in the U.K. despatch samples of quality control material to participant laboratories at frequent intervals to assess laboratory performance. We show, via a controlled experiment on the plasma progesterone assay, that the current analysis performed by the external assessors is inadequate and often leads to erroneous conclusions about a laboratory's performance. It is concluded that for a proper assessment of a laboratory's performance, the external assessor should prepare large pools of plasma and distribute them to all participants in the scheme to use as internal quality control material.
mesh_terms: D002623:Chemistry Techniques, Analytical; D006801:Humans; D007753:Laboratories; D011374:Progesterone / Q000097:blood*; D011786:Quality Control; D012015:Reference Standards
chemical_list: D011374:Progesterone