FAQ

  1. Do you provide instructions how to perform PCR?
    30/04/2014

    Event-specific detection methods submitted under the provision of Art. 47 of Regulation EC 1829/2003 and their validation reports are accessible on the web site of the EURL for GM food and feed (EURL-GMFF) under the section "Status of dossiers". Detection methods used during the certification of a GMO reference material are listed in the certification report.

    Institutes: IRMM
    Keywords: GMO, reference material, measurement, quality, standard
  2. Which DNA extraction method should I use?
    30/04/2014

    Reliable results can only be guaranteed if an extraction method validated in a collaborative trial is used. Some extraction methods and their validation reports are accessible on the web site of the EURL for GM food and feed under the section "Status of dossiers".

    Institutes: IRMM
    Keywords: GMO, reference material, measurement, quality, standard
  3. Is the sequence information for GM varieties publicly available?
    30/04/2014

    The sequence information is usually patented by the producer and can in some cases be retrieved from the patent application. The sequence information itself is confidential and therefore not always accessible, whereas the primer and probe sequences targeted by the event-specific detection methods provided according to Art. 47 of Regulation EC 1829/2003 are accessible on the web site of the EURL for GM food and feed under the section "Methods database".

    Institutes: IRMM
    Keywords: GMO, reference material, measurement, quality, standard
  4. Can I purchase 100% GMO CRMs?
    30/04/2014

    IRMM only produces for selected GMO events a pure certified GMO reference material (nominal 100%). However, such materials may be available from other organisations or the intellectual property owner of the GMO event.

    Institutes: IRMM
    Keywords: GMO, reference material, measurement, quality, standard
  5. Can I use the GMO CRMs to calibrate my ELISA measurements?
    30/04/2014

    GMO reference materials from IRMM can be used as calibrants for DNA-based and protein-based methods. You should set-up a calibration with a reference material (calibrant) with known GM concentrations in order to be able to translate your test result into GM% m/m (mass fraction).

    Institutes: IRMM
    Keywords: GMO, reference material, measurement, quality, standard
  6. How to calculate the measurement uncertainty of PCR measurements?
    30/04/2014

    In the Guidance Document on Measurement Uncertainty for GMO Testing Laboratories two selected approaches for the estimation of measurement uncertainty are proposed. The first approach presented in detail is using data from collaborative trial in combination with in-house quality control data. In case no suitable collaborative trial data are available, an alternative approach, using data obtained on within-laboratory samples, is presented.

    Are the GMO CRMs of IRMM checked for the presence/absence of other GM events than the one certified?

    The GMO CRMs are gravimetric mixtures of pure GM and non-GM powders certified for a specific GM event as mass fraction (g/kg). IRMM verifies the purity of the two raw materials used for production with respect to the presence of the particular GM event that is certified. The CRMs are not certified for the absence or adventitious presence of other (contaminating) GM events.

    The GMO CRMs can be used as positive controls for the certified GM event for instance to validate a screening method. However, the GMO CRMs should not be used as negative controls for any other GM event than the one certified. Also the blank material of each series is certified to contain less than the certified amount for a given GM event and the absence of this event can not be guaranteed.

    For additional information IRMM has conducted a study to verify the GM composition of 33 raw materials used for the production of the GMO CRMs. Those raw materials have been tested by quantitative PCR for the presence/absence of 39 single GM targets known for 7 plant species. It needs to be noted that adventitious presence of other GM events is likely to be heterogeneously distributed over the batch of raw material and needs to be taken into account when comparing the results obtained so far. These results are summarised in this document file [70 KB] and provide an indication about possible adventitious presence.

    Institutes: IRMM
    Keywords: GMO, reference material, measurement, quality, standard
  7. How do I compare my result with the certified values?
    30/04/2014

    The underlying principle is that one has to check whether the difference between the measured result and the certified value is larger than the expanded combined uncertainty of measurement and certified value. This is done as follows:

    1. Calculate the standard uncertainty of the certified value (uCRM). This is obtained by dividing the expanded uncertainty given on the certificate by the expansion factor (also stated on the certificate).
    2. Estimate the measurement uncertainty (um) of the result. As a very rough approximation, the reproducibility standard deviation can be used
    3. Combine the two uncertainties: image002.gif
    4. Check whether 2*uc is larger than the difference between the certified and the measurement value. If this is the case, the measurement result agrees within the limits of the respective uncertainties with the certified values

    For example: Certified reference material BCR-605 (road dust) with a trimethyllead-content of 7.9 ± 1.2 µg/kg has been used. The analytical result was 11.10 µg/kg and the standard measurement uncertainty as determined in the method validation (um) is 15 %, i.e. 1.67 µg/kg. The difference between analytical result and certified value is therefore 3.2 µg/kg. Prior to the determination of the combined uncertainty, the standard uncertainty of the certified value of the reference material must be determined. The uncertainty of the certified value (UCRM) is given as 95 % confidence interval with 6 degrees of freedom as stated on the certificate. The factor of the t-distribution (t95, 6) is 2.447. The confidence interval must be divided by this factor to obtain the standard uncertainty of the certified value. This standard uncertainty (uCRM) is therefore:

    image004.gif

    The combined uncertainty (uc) of measurement and certified value is the square root of the quadratic sum of the individual uncertainties:

    image006.gif

    The results show that the uncertainty of the certified value has almost no influence on the combined uncertainty. This combined uncertainty is now multiplied with a coverage factor of 2 to obtain the expanded uncertainty (here 3.48 µg/kg). This expanded uncertainty is bigger than the difference between analytical results and certified values (3.2 µg/kg). Within the limits of the uncertainties, no method bias is visible.

    Institutes: IRMM
    Keywords: reference material, measurement, quality, standard
  8. What is a nominal value?
    30/04/2014

    A nominal value is a provisional value, usually the target one wants to achieve with the CRM. It is usually different from the certified value and should therefore not be used.

    Institutes: IRMM
    Keywords: reference material, measurement, quality, standard
  9. How should I use the data obtained on measurements of a CRM?
    30/04/2014

    There are different possibilities to use the data obtained on a measurement of a CRM. It can be used to help to:

    • validate a method of measurement. This is to see, if the observed value and the certified value match within the uncertainty.
    • verify a specific measurement procedure. This is to see, if the observed value and the certified value match within the uncertainty under the specific laboratory conditions.
    • control the accuracy of measurements within the uncertainty.
    • calibrate a measurement device for a specific type of measurement. This is to establish the relation between a ‘signal’ and the quantity intended to be measured (usually a concentration). In the simple case, a calibration factor and its uncertainty is calculated from the observed value and the certified value.
    • establish proficiency testing. The use of a well characterised (i.e. certified) material in form of a ‘blind sample’ is advantageous, in order to monitoring against a stated reference, in particular the inalterable SI being stable in time and space.
    • develop new methods of measurement.
    • estimate measurement uncertainty.
    Institutes: IRMM
    Keywords: reference material, measurement, quality, standard
  10. How reliable is my measurement result?
    30/04/2014

    The reliability of the method applied has to be demonstrated by means such as method validation, proper use of quality assurance tools (including the use of CRMs) and the participation in proficiency testing.

    Institutes: IRMM
    Keywords: reference material, measurement, quality, standard