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.
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