- Abstract The use of proficiency testing schemes (PTS) by laboratories as an integral part of their quality
system has been increasing in recent years. Accreditation bodies, regulators and the laboratories customers
are increasingly using results from PTS in their relationship with laboratories. There are many PTS available in
Europe in analytical chemistry; EPTIS indicates over 400. The comparability of these PTS is now a real issue,
as many organisers of PTS move into new markets. The COEPT project has systematically demonstrated (in four
technical sectors water, soil, food and occupational hygiene), that there are many similarities between PTS in
each sector. For example, nearly all use the z-score as a performance index. One significant difference between
many PTS is the value used for the term s in the z-score equation, and this gives a range of evaluations for the
same data point. Despite this, the agreement between PTS in the same sector for the evaluation of data isAbstract The use of proficiency testing schemes (PTS) by laboratories as an integral part of their quality
system has been increasing in recent years. Accreditation bodies, regulators and the laboratories customers
are increasingly using results from PTS in their relationship with laboratories. There are many PTS available in
Europe in analytical chemistry; EPTIS indicates over 400. The comparability of these PTS is now a real issue,
as many organisers of PTS move into new markets. The COEPT project has systematically demonstrated (in four
technical sectors water, soil, food and occupational hygiene), that there are many similarities between PTS in
each sector. For example, nearly all use the z-score as a performance index. One significant difference between
many PTS is the value used for the term s in the z-score equation, and this gives a range of evaluations for the
same data point. Despite this, the agreement between PTS in the same sector for the evaluation of data is
approximately 85%. COEPT has given us a basis for establishing the comparability of PTS and showing us where
further harmonisation could occur.…