Intercomparison programmes: a powerful tool of quality control of laboratories

This tool is also a high potential for improvement by forcing the laboratory, to unsatisfactory results, to test their ability to detect potential sources of error, as shortcomings in the qualifications of the staff, the incomplete validation of the test procedure or a one-off error in the operation of the equipment, among others.

The importance and the development of this powerful tool of quality control is such that today already no one questions its use and there are already many sectors, environmental, clinical, food, etc., which use it regularly, which has led to the emergence of a large number of suppliers of intercomparison exercises on the market.

In this sense to the international organizations of acreditadores ILAC (International Laboratory Accreditacion Cooperation) and EA (European Co-Operation for Accreditation) have established policies in this area to understand that, from the viewpoint of the acreditadores, the participation in such programmes is a suitable method of obtaining information about the performance of the laboratory that can be used within evaluation activities set out in the process of accreditation.

However, an intercomparison exercise to perform all its potential improvement for the laboratory and control is imperative that the entire management of the exercise, since the preparation of the sample, send it to the participants and the exploitation and interpretation of datais made with a high level of technical competence. Participation in intercomparison exercises which does not ensure the level is an expenditure of time and money for laboratories which must be avoided.

And it is in this environment when appear first schemes of accreditation of providers of intercomparison programs as a tool for selection according to criteria of quality and technical competence. This type of accreditation arose originally in Australia but quickly they extend to the rest of the world being a reality in ENAC since 2002.

The international situation has evolved much in recent years, being already a fact that a significant number of suppliers both at European and world level are accredited. In fact EPTIS-European Proficiency Testing Information System (www.eptis.bam.de), the largest centre of information on intercomparison exercises already enables differentiated between accredited and non-accredited providers.

Currently it is not usual practice accreditation bodies require laboratories that use providers accredited. However, not should be ruled out that this might be a requirement of national organizations of accreditation in the future, especially when establishing the corresponding agreement of mutual recognition concerning providers of programs of intercomparison, something that will probably be a reality in the short or medium term.

But beyond making or not a requirement, the use of accredited suppliers has other advantages, such as the fact that laboratories that use them do not need to develop a methodology or invest resources to assess suppliers, to able to rely on the evaluation carried out by the accreditation bodies. Not to mention that in carrying out the evaluation by professional experts contribute to increase the level of quality of existing programmes, and therefore confidence in the results.

Therefore, from ENAC we believe essential to promote a more professional and systematic of this tool, use for which it is necessary that laboratories established policies and robust procedures in relation to the evaluation of the quality of the exercises involving of the reliability of their results, taking into account the advantages of using accredited providers where they exist

In this sense, the intercomparison more increasingly as an activity that can contribute not only as a means to verify the quality of the test methods, but to evaluate the skills of analysts, identify biases which may not detect it with programmes of quality control intralaboratorio and even monitor the evolution of methods of trial over time.

Also, and by analyzing the content (statistical results, methods, charts, tables, etc.) of the reports that provide the organizers of the exercises, the laboratory can compare the quality of their trials with other laboratories that have differences in the process or any of the stages of the sameas well as information on other specific aspects of its methods of work, such as the methodologies with minor biases in complex matrices; the biases associated with the different techniques; If methods employing the laboratory are those used by most, they are obsolete or, on the other hand are pointers, etc.

In addition, as added value, participation can bring results to studies of accuracy and calculation of uncertainty needed to perform the corresponding validation of methods.

Therefore, if we take into account all these aspects a laboratory should be considered that the benefits and advantages of a well selected, made and studied, participation will always compensate the employee effort.

Between its obligations is, beyond of a system of quality, very demanding technical requirements such as characterization and study of homogeneity and stability of the sample. All these previous trials are carried out under the criteria of the ISO 17025 standard, which implies a major technical and economic effort with the ultimate goal of providing all of the participating laboratories samples identical, primary basis on which a good intercomparison exercise must be based. Finally the use of statistical techniques tested by the Organizer provides results participants which compared with sufficient guarantees so that they can use in your daily work without doubt whether the rule that are measured is the appropriate.

In short, the participation in accredited intercomparison exercises is the best medium with which to compare our results and know the quality of the service that we offer to our customers.

Iñaki Eguileor, Member of the Scientific Committee of the Laboratory Science Central, Executive Agency of the Department of food, environment and Rural Affairs of the British Government, provider of accredited intercomparison exercises

One of the main concerns of the laboratories, and its customers, is to know if their results are comparable with other laboratories from its field of activity. Various sectors even require satisfactory participation in intercomparison exercises (EI) as a requirement to carry out their activities.

The standard ISO 13528 and the international harmonized Protocol of IUPAC reflect improvements in methodologies to develop the proficiency tests, including the statistical evaluation of results and the quality of the materials used. Also, the widespread use of benchmarks for evaluation of the performance, as the z-score, facilitates the interpretation of the quality (bias and accuracy) of the results of a laboratory regardless of the sector and activity evaluated.

However, the main developments in recent years has been moving from a simple description of the quality offered by the laboratories, the so-called "quality prevalent", try to know if the results provided by the laboratories, as well as comparableIt is appropriate to allow the appropriate decisions to be taken. An evaluation with quality objectives appropriate to the intended purpose has become the biggest challenge of the suppliers of EI.

For laboratories to the selection of appropriate EI, which are genuine tools for its improvement and effectively complement their internal quality control. To this end, in addition to the frequent participation with materials similar to the real and varied, they must find clear reports that reflect the use of appropriate evaluation criteria. Thus they endorse the requirements that were set in the validation of their methods getting objective elements to improve