Commutability of food microbiology proficiency testing samples
Article first published online: 9 DEC 2013
© 2013 The Society for Applied Microbiology
Journal of Applied Microbiology
Volume 116, Issue 3, pages 612–619, March 2014
How to Cite
Abdelmassih, M., Polet, M., Goffaux, M.-J., Planchon, V., Dierick, K. and Mahillon, J. (2014), Commutability of food microbiology proficiency testing samples. Journal of Applied Microbiology, 116: 612–619. doi: 10.1111/jam.12396
- Issue published online: 14 FEB 2014
- Article first published online: 9 DEC 2013
- Accepted manuscript online: 22 NOV 2013 07:04AM EST
- Manuscript Accepted: 16 NOV 2013
- Manuscript Revised: 7 NOV 2013
- Manuscript Received: 14 AUG 2013
- Walloon Region (DGARNE)
- Belgian Agency for the Safety of the Food Chain
- Université catholique de Louvain (UCL)
- food microbiology;
- matrix effect;
- proficiency testing;
Food microbiology proficiency testing (PT) is a useful tool to assess the analytical performances among laboratories. PT items should be close to routine samples to accurately evaluate the acceptability of the methods. However, most PT providers distribute exclusively artificial samples such as reference materials or irradiated foods. This raises the issue of the suitability of these samples because the equivalence—or ‘commutability’—between results obtained on artificial vs. authentic food samples has not been demonstrated. In the clinical field, the use of noncommutable PT samples has led to erroneous evaluation of the performances when different analytical methods were used. This study aimed to provide a first assessment of the commutability of samples distributed in food microbiology PT.
Methods and Results
REQUASUD and IPH organized 13 food microbiology PTs including 10–28 participants. Three types of PT items were used: genuine food samples, sterile food samples and reference materials. The commutability of the artificial samples (reference material or sterile samples) was assessed by plotting the distribution of the results on natural and artificial PT samples. This comparison highlighted matrix-correlated issues when nonfood matrices, such as reference materials, were used. Artificially inoculated food samples, on the other hand, raised only isolated commutability issues.
In the organization of a PT-scheme, authentic or artificially inoculated food samples are necessary to accurately evaluate the analytical performances. Reference materials, used as PT items because of their convenience, may present commutability issues leading to inaccurate penalizing conclusions for methods that would have provided accurate results on food samples.
Significance and Impact of the Study
For the first time, the commutability of food microbiology PT samples was investigated. The nature of the samples provided by the organizer turned out to be an important factor because matrix effects can impact on the analytical results.