Objective and organisation

Laboratory performance studies are organised by private or public entities. Participation can be done on a voluntary basis (e.g. by subscription). It may be mandatory when the laboratory seeks for a special recognition or social status e.g. accreditation. The number of participants may vary from some 20 e.g. for some very specialised measurements such as doping control laboratories of the International Olympic Committee (IOC) to nearly hundred or more, e.g. in the case of the QUASI M EM E project described in section 12.5.6. 

To have a real impact on the quality of the laboratory performance the participation in interlaboratory performance studies should be done on a regular basis and should be an integral part of the laboratory quality assurance and quality control system. The common project of lUPAC/AOAC/ISO, leading to a harmonised protocol [3] gives several indications and recommendations on the organisation and evaluation of such interlaboratory studies. 

The study may concern prescribed (e.g. normalised) methods or the participants may apply their own preferred method. The study involves on a regular basis the distribution of samples to the participants. The frequency of the trials will depend on the type of determination requested, e.g. the difficulty and duration of the determina-tion(s), the frequency of such analyses in the laboratory, the cost/benefit of the test, the duration of the treatment of the data which is influenced mainly by the number of participants and the number of samples to be prepared. Too frequent exercises e.g. more than twice a month, would be inefficient as the laboratory would have no time to evaluate the results between trials. Too long delays between exercises e.g. once a year, does not allow to estimate trends in performance and would be of little help in the laboratories quality control schemes. 

To avoid too long delays between trials the number of participants may be limited. The data should be sent back by the participant in a given short time interval and the outcome of the exercise should be made available as soon as possible together with an advice to poor performers. This allows the participants to take appropriate action in time. 

Whatever the frequency and content of the studies will be it has to be clear before 

---