FDA warns of false negative results for food allergies after skin testing

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All skin tests doctors commonly use to check for food allergies may provide false negative results, the Food and Drug Administration has concluded — meaning people with potentially life-threatening allergies could be mistakenly diagnosed. that they are not at risk. The tests will now be required to include a warning urging doctors to consider retesting the test with more accurate approaches.

The FDA’s new mandatory warning, announced Friday, comes after a December recall of some skin tests used to test for food allergies.

At the time, the FDA said it had received “increased” reports of false negatives from certain lots of extracts manufactured by ALK-Abello that are used to diagnose peanut allergies.

However, the FDA now says that these false negative results are not an isolated issue.

ALK-Abello and competitor Greer Laboratories were asked to update the labeling for all of their skin allergy tests to include a new warning that “confirmation of a negative skin test with blood tests or supervised oral food challenges” from providers urges you to consider doing”.

“FDA has determined that the risk of anaphylaxis following a false negative food allergen skin test result applies to all allergenic extracts for the diagnosis of food allergy,” the agency said in a statement.

Anaphylaxis is a severe allergic reaction that can include a sudden drop in blood pressure and difficulty breathing. It can be treated with a shot of epinephrine, but can be life-threatening without rapid medical intervention.

Some liquid extracts used to test for allergic reactions, such as cat hair or dust mites, are standardized to meet some agreed benchmark for potency. However, the FDA says that the drops used to test for food allergies such as peanuts are not.

ALK-Abello and Greer Laboratories did not immediately respond to requests for comment.

An FDA spokesperson did not specify how many reports of life-threatening allergic reactions have been received as a result of false negative food allergy tests.

For the peanut skin test product that was in the FDA’s initial recall, federal data points to 90 cases of false negative results, 17 reports of serious cases, and no deaths.

The skin prick test is a commonly used form of allergy test, in which the doctor administers a specially made extract via prick or shallow injection and then observes within several minutes whether a rash or bumps form. It happens.

The FDA’s move also comes amid the adoption of oral food challenges among allergists, in which patients gradually eat increasing amounts of the suspected allergen — such as a food containing Groundnut – being closely monitored for a reaction.

That approach is considered more accurate, but can be more resource-intensive and riskier to administer.

“For peanuts, milk and eggs in general we say there is a highly reliable negative predictive value of about 95%. But again, there are five percent of patients who can have normally negative skin tests and still have a reaction. do,” Dr. Drew Bird says. A professor of pediatrics at the University of Texas Southwestern Medical Center who researches the treatment and diagnosis of food allergies.

Byrd recently spearheaded the American Academy of Allergy, Asthma and Immunology report, which updates guidance for oral food challenges.

Bird said supervised oral food challenges may be the most conclusive way for doctors to see whether patients are allergic. But the procedure, which can take hours and poses a risk to patients, is typically only used as a later step in allergy diagnosis.

Doctors may also test for elevated levels of specific antibodies to allergens, such as peanuts, in the blood.

However, this option has some drawbacks, Bird said, which may be inaccurate especially when used excessively in patients whose history does not otherwise suggest allergy.

Bird said allergists often use the tests in combination. Those results ultimately determine whether or not to proceed with a food challenge, especially in cases where skin and blood test results are either inconclusive or may be false negatives.

“If testing shows they are likely to react, I don’t need to put them at risk of a food challenge year after year to verify they’re still allergic,” Bird said. “

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