By Heather Hobbs
Laboratory Proficiency Testing – What’s in Your Food?
The recent food industry crisis arising from the use of horsemeat in packaged products has brought into question the capability of analytical procedures to detect adulterated items. Mark Sykes of The Food and Environment Research Agency (Fera) UK, explains Fera’s proficiency testing service to ensure product integrity and how this could rebuild consumer confidence.
If I ask a laboratory to do an analysis for me, how do I know that the laboratory is producing the correct answer? Is it because they have a validated method or that they are accredited to a recognised international standard of quality assurance (ISO 17025, for example)? Or is it because they routinely use internal quality control systems? These are all valid means of ensuring quality assurance but only from an internal perspective. What they lack is a means of comparing their results against an external reference, one that they have no control over.
One method of ensuring that external quality assurance is by participating in a proficiency testing (PT) scheme. PT exists for any number of routine analyses but in the food analysis sector, there is one outstanding scheme. The Food Analysis Performance Assessment Scheme (FAPAS) provides this PT service.
How does PT work in practice? On a pre-scheduled date, FAPAS sends out a test sample to all the laboratories that have signed up to that particular PT. Instructions for sample handling (but not analytical method) are provided via download from the secure area of the FAPAS website. Laboratories then have typically between four and six weeks to carry out their analyses and report the results, again to the FAPAS secure web interface. Laboratories use their own routine methods and can submit details of the methods with the results.
A z-score of zero (0) is exactly correct. z-Scores can deviate positively or negatively and would normally be in the range -2 to +2. All reports give guidance to the interpretation of z-scores and further detail is available in the Protocol.
FAPAS produces several hundred rounds of PT each year, with customers in over 120 countries worldwide. There are four major schemes – FAPAS® (food chemistry), FEPAS®
modified materials analysis) and LEAP®
(food microbiology), GeMMA (genetically (drinking water and environmental
scheme). FAPAS also runs bespoke PT schemes for laboratories with particular requirements that are not necessarily part of the scheduled PTs.
A report of the proficiency test results is then produced. Laboratories can download any reports that they have participated in. The report is completely anonymous, laboratories are identified only by a unique number. The report provides assessments for quantitative results in the form of a z-score. The statistical process used to derive z-scores is explained in each report, in conjunction with the FAPAS Protocol (which can be freely downloaded from the website).
Pictures courtesy The Food and Environment Research Agency (Fera), Crown Copyright Find out more circle no. 10
Following completion of a PT, the remaining test samples are often available to purchase as quality control (QC) samples. These offer a cost-effective means of procuring real food test items for a laboratory’s internal QC management. These come with a specification sheet, detailing the parameters that have been characterised during the course of the PT.
For further information and to register, log on to:
www.fapas.com or email us at
info@fapas.com
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