The European Union Reference Laboratory for Genetically Modified Food and Feed (EU-RL GMFF), accredited under ISO 17043, organised a comparative testing (CT) round for National Reference Laboratories (NRLs) nominated under Regulation (EC) No 882/2004, with voluntary participation of other official control laboratories.
The test items consisted of biscuit powder made from conventional maize and wheat grain spiked with powder of 98140 maize and MON 863 X MON 810 maize in different concentrations (Level 1 and 2). Participants were required to perform species identification and test for the presence of maize events 3272, Bt11, Bt176, 59122, GA21, MIR604, MON 810, MON 863, NK603, 1507, MON 88017, MON 89034, 98140 and MIR162 in the two test items. Any event detected then had to be quantified. Results could be reported in mass/mass % or copy/copy % and the EU-RL calculated the robust means (R) of Level 1 and 2 test items accordingly. The target standard deviation for CT was fixed by the Advisory Board for Comparative Testing at 0.20 for all events, based on the experience of previous CT rounds. The robust means and target standard deviation were used to derive z-scores for the participants’ results.
Sixty-four laboratories from 28 countries registered for this CT round, of which all but one returned at least qualitative test results.
The EU-RL GMFF issued a final report on this CT round in April 2014. After the final report was prepared, it was discovered that the distribution of the quantitative data obtained from laboratories for event MON 863 deviated from normality because some laboratories used the adh1 reference gene (with target amplicon of 70 bp) for quantification of MON 863 maize, which is known to carry a nucleotide polymorphism that may affect amplification. Therefore, the robust means for event MON 863 were re-calculated based on the data from laboratories that had used a reference gene different from adh1-70 bp. The original final report has been re-called; the current version contains the re-calculated z-scores for maize event MON 863.
When performing species identification, almost all laboratories correctly identified maize species in each test item. In addition, approximately half of laboratories also identified soybean and a few oilseed rape.
The majority of laboratories correctly detected the three GM events included in the Level 1 and Level 2 test samples. Results of the quantitative evaluation of the GM content were compromised by the use of the adh1 gene for MON 863 quantification by a number of laboratories. Forty five laboratories (71 %) obtained satisfactory z-scores (|z| ≤ 2.0) for the three GM events in both test items. Among the remaining 18 laboratories, half had unsatisfactory z-scores for MON 863.
Only 46 % of participants provided information on measurement uncertainty in a complete and consistent manner and further improvement in this crucial area is needed.