GMO food/feed testing is based on some fundamental principles of genetic engineering and cellular physiology:
- DNA: The introduction of foreign DNA into a recipient plant’s DNA (genetic engineering)
- Protein: The information coded in DNA is translated into protein that performs the function specified by the DNA instructions (cellular physiology)
Two methods have been developed based on these fundamentals: genetic analysis (DNA analysis) and Immunological analysis (Protein analysis). Three tests are currently available using these methods.
Genetic Analysis (DNA analysis)
Genetic analysis is a GMO testing method that detects the presence of a transgene in a plant cell’s genome. The specific GMO test used in this method is called the polymerase chain reaction (PCR) test.
Polymerase Chain Reaction (PCR Test):
- Copies a specific section of a plant’s DNA billions of times in order to detect and quantitate foreign DNA (GMO) inserted into the plant’s genome.
- Uses short pieces of DNA (primers) that are complementary to the GMO sequence to vastly amplify and quantitate GMOs.
- Performed in a laboratory setting.
- Appropriate for qualitative or quantitative testing.
- Highly sensitive and specific.
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Immuno-analysis (Protein analysis)
Immunological analysis, or immuno-analysis for short, is a GMO test method that detects proteins. Currently, there are two types of GMO tests that use this method: the Strip Test and ELISA Method.
Strip test (Lateral Flow Device or Dipstick):
- A rapid antibody-based method used for measuring GMO protein in unprocessed material such as seed, grain, or leaves
- Uses a detection surface comprised of immobilized GMO protein-specific antibodies on a solid strip
- Appropriate for qualitative or semi-quantitative testing
- Suitable for field testing
ELISA Test (Enzyme-Linked Immunosorbent Assay)
- An antibody-based method for measuring GMO protein in unprocessed material such as seed, grain, or leaves
- Uses a detection surface comprised of immobilized GMO protein-specific antibodies in a multi-well solid plate format
- Appropriate for qualitative or quantitative testing
- Performed in a laboratory setting
Determining which type of GMO test is most appropriate depends on several factors, including but not limited to:
- Nature of the sample
- GMO(s) to be analyzed
- Required test sensitivity
- Whether qualitative or quantitative analysis is required
- Product’s intended market
The chart below summarizes GMO testing options, including the advantages and disadvantages of each method.
GMO testing options
| Analysis | Test | Measures | Advantages | Disadvantages |
| Immunologic |
Strip
test
|
Protein | Because the test is rapid and can be performed on- site, this method is very useful as an initial screen for seed and grain |
Often low sensitivity (Limit of detection 0.1 – 1%) |
| Because the test is not performed with laboratory controls, operator error resulting in inaccurate test results can sometimes be an issue. |
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| Not appropriate for processed products |
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| GM protein levels may vary between different commercial GM cultivars and different parts of the same GM plant |
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| ELISA | Protein | High sensitivity (Limit of detection 0.01 – 0.1%) |
Not appropriate for processed products |
|
| GM protein levels may vary between different commercial GM cultivars and different parts of the same GM plant |
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| Must be performed in a laboratory |
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| Genetic | PCR | DNA | High sensitivity (limit of detection 0.01%) and specificity |
Must be performed in a laboratory |
| Capable of detecting all GMOs |
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| Allows definitive quantification |
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| Effective with broad range of sample types |
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| Industry standard used worldwide in surveillance and testing labs |