HK01 published an article earlier this month, sharing their reporter’s personal experience in using food-specific immunoglobulin G (IgG) testing as a way to lose weight. Through diagnosing food allergy and intolerance with the test, followed by avoiding consumption of certain – the reporter claimed she had lost 20 pounds in three months.

As described by the reporter, the test only required drawing less than 10ml of her blood, while the report was available in around 20 days. The report also indicated the level of food-induced hypersensitivities per each food item, so she could decide which ones to avoid, for the elimination diet.

Although the reporter comments IgG is worth a try, particularly for those who wish to lose weight but to no avail, despite regimented diet and exercise routines. The article emphasised that they are not suggesting it is better to replace immunoglobulin E (IgE) testing with IgG. In addition, readers should consult doctors’ professional opinions, since it is not a scientific article.

Despite the clarification, the article came under fire after it was published. The Hong Kong Allergy Association responded on their Facebook page, claiming the coverage “is inaccurate, and might mislead consumers in believing IgG testing is effective in the diagnosis of food allergy and intolerance.”

Wrong use of IgG test may lead to false diagnoses with severe consequences

The association further commented that there is no existing study attesting to food allergies would result in gaining weight. Rather, avoiding food consumption unnecessarily could lead to severe malnutrition.

The association also warned the public of the danger of relying on the use of such invalidated and unproven tests to tackle food-related disorders – reiterating the fact that IgG testing lacks both a sound scientific rationale and evidence of effectiveness in the diagnosis of food allergy and intolerance.

To further explain the consequences, it shared a commentary published by the Hong Kong Institute of Allergy (HKIA) in Hong Kong Medical Journal in August 2017.

The commentary featured a case of a 3-year-old boy who had almost died due to false diagnoses resulted from an inappropriate use of IgG test. At around eight months of age, the boy was diagnosed with immediate hypersensitivity to milk. Symptoms of his allergic reactions include generalised urticaria, vomiting, and signs of respiratory distress.

Although the child’s parents were advised not to feed him with any dairy products at the moment, his mother took him for homeopathic treatment, which claimed to be able to eliminate food allergies. After the treatment, the mother took her child for an IgG test, which failed to show sensitivity to cow’s milk in its results. The mother, thus thought that food allergy was eliminated – and proceeded to give milk to her boy. The boy immediately developed severe anaphylaxis, and was luckily resuscitated when he was sent to the emergency department.

The company which provided the test, which had not been evaluated by the Food and Drug Administration (FDA), later informed the mother that the test would not show a positive result if the boy had been avoiding the food.

Additionally, HKIA highlighted the possible consequence of unnecessary food avoidance in early life, which may lead to the loss of tolerance and facilitate onset of allergic disease. On the contrary, early introduction of solid foods while still breastfeeding might induce tolerance and lower a child’s subsequent risk of developing atopic disease.

Regulation of immunoglobulin G testing

The American Academy of Allergy, Asthma & Immunology also commented that IgG and IgG subclass antibody tests for food allergy do not have clinical relevance, are not validated, lack sufficient quality control, and should not be performed.

In Hong Kong, these types of tests remain in a legal grey zone. An imported pharmaceutical must obtain regulatory approval in its country of origin before it can be licensed locally. Nevertheless, there is no such rule for laboratory tests; and hence, this remains a free market for all.

Patients with suspected food-related disorders should seek guidance from a physician for diagnostic testing and interpretation of test results. Measurement of food-specific IgG concentrations to diagnose food allergies and intolerance is strongly discouraged.

General practitioners are encouraged to consult their allergy and immunology colleagues if there is any uncertainty about the appropriate management steps for these patients, as unnecessary elimination of foods can lead to severe malnutrition – and possibly result in death. MIMS

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