Previous studies have shown that the type and level of quality assurance which takes place in many analytical laboratories does not extend significantly to measurements made outside the laboratory. One valuable quality assurance tool used by laboratories which could be adapted for out-of-laboratory measurements is proficiency testing. The data produced by proficiency testing, although primarily aimed at helping individual laboratories or organisations to monitor and improve the quality of their measurements, is invaluable for assessing the efficacy of test methods and equipment. It is also useful for identifying measurement problems which affect all participants, and providing a basis for collaborative action to address such problems.

The establishment of proficiency testing for out-of-laboratory measurements is considered to be feasible and consultation amongst interested parties has reinforced the need for and identified support for the development of a prototype scheme. Out-of-laboratory proficiency testing has potential to provide benefits not only to those making measurements, but also to the manufacturers and suppliers of portable measuring equipment and the users of analytical data.

For environmental measurements, the greatest analytical challenges lie in establishing a proficiency testing scheme covering the field analysis of soil and it is recommended that a prototype scheme covering out-of-laboratory measurements in the contaminated land sector be developed under the VAM Out-of-Laboratory Measurements Project.