The Need for a Standardized Sample Portion When Testing Food for Gluten Using an LFD: A Case Study

The Need for a Standardized Sample Portion When Testing Food for Gluten Using an LFD: A Case Study

Gluten Free Watchdog along with Adrian Rogers, Bio-Check (UK), and Luke Emerson-Mason (Bia Diagnostics) recently presented an abstract and poster at the AOAC International annual meeting.

The abstract and poster are based on testing of Liquid I.V. Hydration Multiplier Strawberry.

View full size poster HERE.

Abstract: Consumers with celiac disease have access to lateral flow devices (LFDs) to test food for gluten. Erroneous results may occur due to matrix effects and sampling that can cause confusion among consumers and lead to online criticism of food manufacturers. LFD kit manufacturers should provide clear user instructions, such as those specified in AOAC’s Stakeholders’ Guidance Document for Consumer Analytical Devices. Gluten Free Watchdog received many complaints about a labeled gluten-free powdered drink testing positive for gluten using at least two LFDs. A consumer’s retained sample and a new box of product were tested by Bia Diagnostics using the sandwich R5 ELISA, competitive R5 ELISA, and LFD test strips. 0.5-gram samples and the amount in a level, kit-provided scoop were analyzed (kit instructions state either amount can be used). The pH of a 0.5-gram sample and a level scoop also were assessed along with buffer solution controls. The consumer sample read <5 mg/kg with the sandwich R5 ELISA, <10 mg/kg gluten with the competitive R5 ELISA, and negative for gluten with the LFD when 0.5-g samples were tested. The purchased sample gave similar results. There was no detectable gluten in either sample. When level scoops of sample were tested, results were positive. A level scoop of product weighed approximately twice as much as recommended for testing. A 0.5-gram sample of product was pH 6.04. A level scoop of product was pH 4.83. Buffer solutions at pH 4 and 7 tested positive and negative for gluten, respectively. False positive results may occur when consumers use LFDs to test food for gluten. Consumers should be advised to use a specified weight of product. They should be cautioned that testing a lower or higher weight may cause inaccurate results.

Please reach out with any questions.

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Comments (5)

  • Samantha Frohwirth Reply

    Is there a way to make the conclusion easier for the average person to understand? Is there gluten in liquid IV or not? Because I drink those all the time

    August 31, 2022 at 6:18 pm
    • Tricia Thompson Reply

      At this point, all we have posted is the abstract and poster from AOAC. My recommendation is to read the results and the conclusion on the poster, including text in red that reads, “All samples tested using the sandwich or competitive R5 ELISAs also tested below the limit of detection for each assay (1 mg/kg (ppm) of gluten for the sandwich, 4.6 mg/kg (ppm) for the competitive— no detectable gluten was present in the samples tested)

      August 31, 2022 at 6:22 pm
  • Leah Reply

    I concur with the above observation that this poster’s conclusion section could benefit from increased clarity. I may try to find a way to reach out to the researcher, but just in case anyone is able to answer my question here I thought I’d post it here as well 🙂 I may very well just be missing something (I’m newly diagnosed and still learning). As far as we know, do the results suggest that using a level scoop leads to false positive because that quantity is not a quantity that is able to accurately tested no matter the substance being tested or is it suggesting that at smaller quantities the powder tests below 20 ppm but that if one were to consume multiple liquid IVs throughout the day, surpassing the amount of powder in a level scoop, they would be consuming too much gluten to be safe? I ask because many people with POTS, myself included, have celiac disease or gluten intolerance. We also are instructed to consume multiple oral rehydration solutions a day, liquid IV being one of the few suitable options for medical consumption. Liquid IV offers a discount to those with POTS or other dysautonomias, so many of us drink quantities of this far beyond what an average consumer would. I was drinking 2-4 of these at least, daily, for weeks. My B vitamin levels are chronically low as are all the other nutrients included, so I doubt I was overdosing on that. I also consume far more vitamin B in my current regimen than I did with liquid IV. I felt so much better once I cut out liquid IV and returned to other options, an experience mirrored by a number of people with both POTS and gf diets. The ingredients in the other options are incredibly similar, the possibility of gluten is the only clearly apparent difference I can see. I’m wondering if the results suggest consuming one liquid IV is fine but multiple puts you above a safe threshold or if they suggest the results are invalid for a different reason. Does anyone have any insight on this? Thanks!

    August 31, 2022 at 7:14 pm
    • Tricia Thompson Reply

      This is one of the researchers–Tricia Thompson. What is posted here is for a scientific audience. We have not had a chance to post a more simplified version (this poster was presented yesterday at AOAC). The issue is pH. The pH of a larger weight amount of product causes false positives when a lateral flow device is used for testing. Testing using ELISAs found no detectable gluten in the samples tested.

      August 31, 2022 at 7:27 pm
      • Leah Reply

        This is very helpful and clarifying—thank you for taking the time to explain. That’s definitely interesting about the pH, and I apologize if I missed something obvious. Learning all this new lingo and the various guidelines is a lot, especially when the brain fog hasn’t quite subsided yet, and it’s one reason I’m so thankful for this site! I guess the liquid IV mystery remains a mystery for me, haha, but I’m relieved to know that gluten is not culprit!

        August 31, 2022 at 11:04 pm

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