Economy of proficiency testing: reference versus consensus values

Many proficiency tests are operated with a consensus value derived from the participants' results. Apart from technical issues, one of the reasons oft en mentioned is that proficiency tests operated with consensus values would be cheaper than those using reference values obtained from a priori charac terisation measurements. The economy of a proficiency test must of course b e balanced by the need of the participants, and the quality of the comparis on in general. The proficiency tests selected in this study had both a refe rence value and a consensus value, one of which was used for assessing the performance of the participating laboratories. In this work, both a technic al and an economical assessment of how the comparisons were operated is mad e. From the evaluation, it follows that usually the use of consensus values does not necessarily reduce the costs of a proficiency test. However, freq uently it may be observed that the quality of the assessment of the laborat ories is better with a reference value.