According to the EURLs Campylobacter-CPS-Lm Guide on the implementation of the Standard EN ISO 19036:2019, matrix uncertainty corresponds to the uncertainty associated with taking the test portion from the laboratory sample; it is therefore different from the uncertainty linked to sampling (taking a sample from a batch of production). It is linked to the degree of the spatial heterogeneity of the microorganisms within the matrix. It is thus expected to be large for solid or multi-component matrices, and low for homogeneous matrices. It is assumed in the standard as being independent of the analytical method used (including target bacteria) and of the laboratory estimating it.

The standard allows using values of matrix uncertainty already obtained for laboratory samples expected to have a similar matrix uncertainty (matrix homogeneity). We thus suggest using values of matrix uncertainty, per matrix type, obtained in a collaborative study organised by the three EURLs Campylobacter, CPS, Lm, together with the associated NRLs networks.

> The values are available here <

The report (V1, 16 June 2022) of the study is available on Zenodo:

The matrix uncertainty values obtained in this collaborative study can be used by any laboratory for the calculation of combined uncertainty when analysing the same matrices or matrices expected to have a similar matrix uncertainty.