What to do if no suitable PT scheme is available

It may happen that a laboratory cannot identify a suitable PT scheme in its own region. However, there are still alternatives which allow an external assessment of its measurement competence. These alternatives include:

The laboratory could participate in a scheme that is organised outside its region, for example check the availability of other schemes through a query in the EPTIS database – many PT schemes are organised on an international basis.

The laboratory can enter into other types of interlaboratory comparisons, including those that are organised for the validation of methods or the certification of a reference material. However these schemes may not always be open to all laboratories.

The laboratory can organise an interlaboratory comparison itself. This does not have to be very complicated and may simply involve an exchange of samples with a peer laboratory – as long as their testing methods are equivalent.

If none of these alternatives can be realised, the laboratory could strengthen those internal QA measures that have an external component, such as the use of certified reference materials and standardised validated methods, and comparison between different methods of analysis.