European Interlaboratory Test Programme (LIFE+/FutMon, ICP-Forests)A series of inter-laboratory comparison tests is an excellent tool for improving the quality of the data produced by the participating laboratories over time. This is because of the training effect in the use of a method, and because the remaining ring test sample material can be used as reference material in the laboratory up until the next ring tests.
Tolerable limits for the deviation of the individual test result from the comparison mean value were selected for each variable measured. Results falling outside the tolerable limits indicate problems in the analytical procedure, or more general quality problems in the laboratory. The tolerable limits were set in order to act as a driving force to reduce measurement uncertainty and increase the comparability of results among the participating laboratories. As a result, the tolerable limits have, in some cases, been adjusted downwards in order to maintain their role as a driver for quality improvement as an increasing number of the laboratories meet this quality requirement. The tolerable limits are listed in the QA/QC paper of the WG QA/QC in labs.
The inter-laboratory comparisons conducted within the framework of the LIFE+/FutMon and the ICP Forests programme are aimed at testing the proficiency of the laboratories, i.e. evaluating the comparability of the results and, if possible, identifying the main causes of errors. The laboratories must be involved in discussions on the outcome of ring tests in order to obtain information useful in achieving, maintaining and optimizing their analytical quality.
Laboratories with unacceptable results in ring tests had to re-qualify and they are invited to participate in assistance program organized by the WG on QA/QC in Laboratories.