Success of accredited laboratories in international proficiency testing agreed in advance is utilised in proving efficiency of accreditation. On the European level, co-ordination of proficiency testing and comparison of results is performed in the proficiency testing working group of the European co-operation for Accreditation, EA. Sufficient number of laboratories from different European countries must take part in the proficiency testing in order for the results to be analysed in a reliable manner.
EA does not organize proficiency testing by itself but co-operates with competent providers of proficiency testing. EA's proficiency testing working group decides on the selection of proficiency testing to be monitored. Accreditation bodies whose task is to select and invite accredited laboratories from their own country to the selected proficiency testing are informed of the decision.
EA processes the proficiency testing confidentially and the providers of proficiency testing do not endanger the confidentiality of their clients' results. In order to have a statistically sufficient number of results that can be analysed and utilised, it is important that an adequate number of laboratories named by EA take part in the testing. In addition to the assessment of accreditation efficiency, technical questions and problems which have arisen in the proficiency testing are processed further. These technical issues are brought to the attention of the accreditation bodies, which can further inform their technical assessors and thus develop the assessment operations.