Advanced Technology in Food Production

ATFP: Human Consumption of Plant Foods Produced Using Genetic Engineering (GE) Technologies (2015)


Batista R, Nunes B, Carmo M, Cardoso C, Jose HS, de Almeida AB, Manique A, Bento L, Ricardo CP, Oliveira MM. Lack of detectable allergenicity of transgenic maize and soya samples. J Allergy Clin Immunol. 2005; 116(2): 403-410.

PubMed ID: 16083797
Study Design:
Non-Randomized Crossover Trial
C - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To compare the IgE response of allergy-sensitive populations to genetically modified (GM) maize and soya products vs. the IgE response to non-modified maize and soya products in the same individuals.
Inclusion Criteria:
  • Positive history of food allergy, inhalant allergy or both
  • Positive skin prick test (SPT) response for related allergens
  • Receiving care at the Hospital of Santa Maria Paediatrics Allergy Department or the University Clinic of Pneumology 
  • Informed consent provided by participant or parents.
Exclusion Criteria:
  • No history of food allergy, inhalant allergy or both
  • Negative SPT response for related allergens.
Description of Study Protocol:


Recruited from clinics at the Paediatrics Allergy Department of the Hospital of Santa Maria and the University Clinic of Pneumology from the Hospital of Santa Maria.


Each study participant completed a food inquiry to determine which maize and soya derived products had been consumed in the past. Skin tests were performed in two human populations with positive histories of food allergy, inhalant allergy or both as well as a SPT response for related allergens. One group was composed of 27 children with food and inhalant allergy and the other group was composed of 50 adults with asthma or rhinitis. The children were tested with extracts of Bt176, Bt11, RUR and non-transgenic analogues and the adults were tested with extracts of MON810, T25 and non-transgenic analogues. Skin tests were performed by using the prick procedure and results were read after 20 minutes. The results were classified as positive when the larger diameter of the wheal exceeded 3mm. Histamine hydrochloride was used as a positive control and phenolate saline serum while glycerine was used as a negative control.

Blinding Used

Implied with measurements.


Skin prick tests with extracts prepared from transgenic maize and soya.

Statistical Analysis

  • Results from food inquiry and the percentage data of maize and soya products with detectable transgenic proteins provided by Instituto de Biologia Experimental e Tecnologica Good Laboratory Practices Microbiology laboratory
  • Number of products with maize or soya consumed by the population is a Poisson random variable and that the probability of an individual having consumed a product with transgenic proteins is modeled using binomial distributions
  • Probability estimated using the mean number of consumed products with maize or soya obtained in the survey and as the proportion of maize and soya products detected with transgenic proteins calculated using the Instituto de Biologia Experimental e Tecnologica Good Laboratory Practices Microbiology laboratory.


Data Collection Summary:

Timing of Measurements

  • Food inquiry performed once to evaluate the consumption of soya and maize food-derived products
  • Skin testing performed once using the prick procedure with results read after 20 minutes
  • IgE immunoblot reactivity assay of sera completed for 57 individuals with positive history of documented food allergy and positive value equal to or higher than Class 3 on specific UniCAP test.

Dependent Variables

  • Skin reaction to SPT; positive result classified as positive when the larger diameter of the wheal exceeded three millimeters
  • IgE immunoblot reactivity assay.

Independent Variables

SPT using protein extracts prepared for transgenic soya (Roundup Ready) or maize (MON810, Bt11, T25, Bt176) samples.

Control Variables

  • Transgenic quality of non-certified flour samples
  • Quality of transgenic proteins in maize and soya extracts
  • Concurrent SPT using nontransgenic control samples.


Description of Actual Data Sample:
  • Initial N: N=106 individuals (48 males, 58 females)
  • Attrition (final N): N=106 individuals (48 males, 58 females).


  • Average age of 12.4 years
  • Less than five years old: 20 subjects
  • Five years to 10 years old: 56 subjects
  • Ten years to 25 years old: 11 subjects
  • Twenty-five years or older: 19 subjects.


Lisbon, Portugal.


Summary of Results:

Key Findings

  • None of the individuals undergoing tests reacted differentially to the transgenic and non-transgenic samples under study
  • None of the volunteers tested presented detectable IgE antibodies against pure transgenic proteins
  • Food inquiry:
    • All 106 individuals consumed some of the 205 products presented with mean consumption of 39.3 maize and soya products
    • Probability of an individual having eaten GM food was near 100%.
  • Allergenicity tests:
    • Skin testing of the two populations:
      • Only individuals with maize sensitivity, soybean sensitivity or both had positive results against protein extracts under testing
      • No participants reacted differently to GM vs. non-GM samples
      • All participants had larger than 3mm wheals for histamine and none reacted against the negative control.
    • IgE immunoblot reactivity assay of sera from patients with food allergy:
      • None of the participants tested presented differential signals against non-transgenic vs. transgenic protein extracts
      • All 24 individuals tested against pure transgenic proteins presented no detectable reactions against these controls.
Variables SPT
Number of Individuals Tested
Positive Responses (%)
IgE Immunoblot Reactive Assay
Number of Individuals Tested
IgE Immunoblot Reactive Assay
Positive Responses (%)
GM protein PAT 77 0 Note tested
GM protein CRY1A(b) 77 0 57 0
CP4EPSPS 27 0 57 0

Other Findings

All samples tested were correctly labeled and cross-contamination was not present.


Author Conclusion:
The transgenic products under testing seem to be safe in terms of allergenic potential. We propose post-market testing as an important screening strategy for putative allergic sensitization to proteins introduced in transgenic plants. The study found no differential positive results; therefore, the conclusion is that transgenic products under testing seem to be safe regarding their allergenic potential.
Funding Source:
Government: Fundacao Calouste Gulbenkian and Comissao de Fomento da Investigacao
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes