Report on the matrix uncertainty study organised by the three EURLs with the NRL networks of Campylobacter, Coagulase Positive Staphylococci and Listeria monocytogenes

Matrix uncertainty, as described in the Standard EN ISO 190361, is the effects of microbial distribution in a given matrix, i.e. the variation between analytical results from different test portions taken from the same laboratory sample when analysed under repeatability conditions.

The matrix uncertainty is expected to be large for solid or multi-component matrices, and low for homogeneous matrices such as liquids and powders. It is assumed in EN ISO 19036 (clauses 6.3 and 6.4) as being independent of the analytical method used (including target bacteria) and of the laboratory estimating it.

A collaborative study was organised in 2021 by the three European Union reference laboratories (EURLs) for Campylobacter, Coagulase Positive Staphylococci (CPS) and Listeria monocytogenes (Lm), together with the associated networks of national reference laboratories (NRLs) to determine matrix uncertainty for certain routinely analysed matrices.