Ten Questions to Ask Before Selecting a GMO Testing Lab

GMO testing labs vary widely in the accuracy, scientific rigor, and quality of their analytical services. The range of performance becomes obvious when one reviews the results of any ring trial or performance assessment study of GMO testing labs.

Selecting a lab is not a trivial decision, because the client must rely on that lab for business-critical information, information that may significantly affect the perception of their products in the marketplace and, consequently, their bottom line.

How to select the “right” lab? The questions outlined below are a good place to start when assessing the promise of any candidate lab.

1. Is the lab accredited to ISO 17025 by a respected third party accreditation organization?

Accreditation to ISO 17025 assures that the laboratory  meets the recognized international standard for analytical laboratories in terms of quality and technical competence. The accreditation process involves the following:

Today’s market is more global than ever and regulatory policy may differ depending on the country, product, and intended use.  In order to ensure maximal market access and options it’s important to use a laboratory that has testing methodologies capable of detecting all commercialized GMOs and that these tests are covered under the laboratory’s scope of accreditation.

3. Do the laboratory’s testing methods operate to highly sensitive limits of detection and quantification? 

A limit of detection of 0.01% is the minimum standard in the industry, and at present, the technical limits of quantitative GMO testing methods set the practical limit of quantification at 0.05% for real-time quantitative PCR. The innovation that has made it possible to improve limits of detection is the improvement of DNA purification procedures such that they more effectively remove PCR inhibitors and thereby make it possible to add larger amounts of DNA to each PCR reaction.

4. Does the laboratory use statistically valid sample sizes?

Highly sensitive limits of detection and quantification are meaningful only if sample sizes analyzed are statistically valid for the limit of detection used. Using sample sizes that are too small is a common cause of false negative test results. For instance, if a lot of corn contains 0.1% GM material, yet the sample size is only 300 g (1000 kernels of corn), there is only a 63% chance that the sample will actually contain even a single kernel of GM corn. In this case, no matter how sensitive and reliable the PCR method is, there is a 37% probability that the analysis will yield a false negative result. A sample size of at least 10,000 kernels is highly recommended for unprocessed grain or beans. For more detailed information about sample sizes, contact one of FoodChain ID Testing‘s Technical Advisors.

5. Does the laboratory offer quantitative GMO analysis by real-time quantitative methodology, as well as conventional qualitative GMO analysis, and can they provide ring-trial (performance assessment) results that demonstrate their proficiency in quantitative PCR?

Real-time PCR provides the most accurate quantitation possible over a wide range of GMO concentrations. This powerful and versatile technique is technically very demanding, however. For this reason, it is important to verify that the laboratory has objectively demonstrated its ability to effectively and accurately carry out real-time PCR analysis. Two methods can be used in this verification. First, check that the lab has accredited its real-time analytical methods to ISO 17025, since such accreditation requires that the lab provide detailed validation data to the accreditation agency. Make sure that the ISO accreditation applies specifically to the real-time quantitative method that they intend to use with your samples. Second, ask the lab to document that they have performed satisfactorily in ring trials conducted by an independent organization, such as the US Department of Agriculture, the UK Food Analysis Performance Assessment Scheme, the American Oil Chemists Society, etc.

6. What approach does the lab use for DNA extraction/purification? Do they use their own methods, or do they use off-the-shelf commercial kits?

Many of the compounds naturally present in foods are actually strong inhibitors of the PCR process. It is essential to remove all such compounds from the DNA preparation before carrying out PCR analysis. If this separation or purification is not effective, the sensitivity of the PCR process will be greatly reduced and there will be increased “noise” in the analytical system. The result will be increased risk of false positive and false negative results. The inhibitor problem is compounded by the fact that foods and agricultural products are chemically highly complex. This means that a DNA extraction procedure that works well for one food will fail to work for another. In essence, it is necessary to customize DNA extraction methods for each kind of food product. The use of off-the-shelf DNA extraction kits, purchased from scientific supply houses will be successful with some kinds of foods, but not others. Thus, custom methods are necessary.

7. What controls does the lab use routinely to detect problems with the sample, such as DNA degradation or the presence of PCR inhibitors? 

Two controls are critical for verifying sample quality. The first is a positive control using primers that target a gene present naturally in all varieties of the species of interest. If PCR amplification is reduced in reactions containing the sample DNA, compared to reactions containing a reference preparation of DNA from the species of interest, it is likely that inhibitors are present and/or the sample DNA is degraded. The second critical control is an internal control accomplished by comparing PCR amplification of a known amount of a defined DNA template, by itself, and in the presence of sample DNA. If the sample DNA preparation contains inhibitors, PCR amplification will be reduced. By comparing the results obtained with the positive control and the internal control, the presence of inhibitors and the occurrence of degradation in the sample DNA can both be evaluated.

8. What precautions does the lab use to ensure consistency in data-interpretation?

The key elements are two: (1) implementation of standard operating procedures for data analysis, as well as for the actual laboratory processes involved in GMO analysis, and (2) thorough training and regular re-training of all analysts to ensure that they apply those operating procedures in a uniform and consistent manner. Standard operating procedures are a given for analytical processes. However, if data interpretation is not standardized just as rigorously as the analytical process, inconsistencies in reporting of results will inevitably arise.

9. Does the laboratory offer high quality, responsive customer support and service?

10. Does the lab provide access to consistent and reliable testing world-wide? 

Food and agricultural exports must frequently pass additional GMO tests conducted thousands of miles apart. If the labs involved test to different standards, conflicting results will frequently arise, creating significant business risk. For companies that operate in the international arena, it is highly useful to work with a lab that has affiliates in many locations around the world, all of which operate to uniform, standardized procedures, and thus assuring consistent testing of products, wherever they are moved around the globe.