External quality assessment schemes and improvements in the measurement of trace elements in biological fluids

Abstract

Developments in analytical techniques and a greater awareness of quality assurance should lead to improvements in the accuracy, precision and general reliability of difficult measurements. The effectiveness of these factors on improvements in the determination of trace elements in biological fluids is shown by results from external quality assessment schemes (EQAS). The changes and innovations to the Guildford Trace Elements EQAS during the last ten years are described. Twenty-three assays in serum, whole blood, urine, dialysis fluids and water are assessed by the scheme. Current performance of individual participants is monitored each month and during the most recent six months. These measures of performance have shown that improvements can be stimulated by a shared policy for internal quality control and the imposition of standards which are indicative of unacceptable analytical data. In the United Kingdom, where these initiatives have been applied to hospital laboratories, the number of participants with poor performance for the measurement of aluminium in serum has fallen from 61% in 1990 to 20% in 1994.