Peds Allergy Tests
New AAP Report: Don’t Rely on Blood Tests to Determine Pediatric Allergies
Print This Post
Allergies are the most frequently reported chronic condition in children, limiting activities for more than 40% of them and are the third most common chronic disease for children younger than 18 years old.[1] However, a new clinical report from the American Academy of Pediatrics (AAP) urges clinicians to use caution when ordering allergy tests and to avoid making a diagnosis based solely on a skin test or the identification of an allergic-specific immunoglobulin.
Published in the January issue of Pediatrics,[2] the authors recommend that you use the results from blood and skin-prick testing only to confirm your clinical suspicions of a child with symptoms—these tests should not be used to test for allergies in patients who are asymptomatic. If a food allergy is suspected, the patient should undergo a food challenge—the gold standard for diagnosis—which involves consuming small doses of the suspected allergen under medical supervision.
Unlike food challenges, which directly measure an actual allergic reaction, skin-prick and blood tests detect the presence of IgE antibodies, which are chemicals released in response to allergens. A positive skin-prick test will produce a large wheal at the injection site; a positive blood test will produce measurable levels of specific IgE antibodies circulating in the blood.
While the tests can help you make a diagnosis, they should be interpreted in the presence of a clinical presentation. According to the AAP report, while both of these tests can identify sensitivity to a substance, they stop short of accurately determining whether or not a child has a full-blown allergy. For example, past research has found that up to 8% of children have a positive skin or blood test for peanut allergies, but only 1% have clinical symptoms.[3] Similarly, caution is advised when testing is negative despite a convincing history. While undiagnosed allergies can be dangerous—or even fatal—overdiagnosis can lead to unnecessary food or environmental restrictions.
The report also says that skin and blood tests can and should be used to
- Confirm a suspected allergic trigger after observing clinical reactions suggestive of an allergy. For example, children with moderate-to-severe asthma should be tested for allergies to common household or environmental triggers including pollen, molds, pet dander, cockroach, mice, or dust mites.
- Monitor the course of established food allergies via periodic testing. Levels of antibodies can help determine whether someone is still allergic, and progressively decreasing levels of antibodies can signify allergy resolution or outgrowing the allergy.
- Confirm an allergy to insect venom following a sting that causes anaphylaxis, a life-threatening allergic reaction marked by difficulty breathing, lightheadedness, dizziness, and hives.
- Determine vaccine allergies (skin tests only).
Conversely, skin and blood tests should NOT be used
- As general screens to look for allergies in symptom-free children
- In children with history of allergic reactions to specific foods. In this case, the test will add no diagnostic value, the experts say
- To test for drug allergies. Generally, blood and skin tests do not detect antibodies to medications
The authors of the report also suggest that you seek outside help as needed. Be prepared to consult with allergist-immunologists with specialized expertise who can help determine whether or not a clinical allergy actually exists and how severe it is.
The bottom line? While allergy tests can be a valuable tool, pediatricians should use them cautiously and judiciously and interpret results in the context of symptoms and history
Jill Shuman, MS, ELS
Published January 4, 2012
References
- Allergy facts and figures. Asthma and Allergy Foundation of America Website. http://www.aafa.org/display.cfm?id=9&sub=30#prev. Accessed January 2, 2012.
- Sicherer SH, Wood RA; the Section on Allergy and Immunology. Allergy testing in childhood: using allergen-specific IgE tests. Pediatrics. 2012;129(1):193-197.
- Liu AH, Jaramillo R, Sicherer SH, et al. National prevalence and risk factors for food allergy and relationship to asthma: results from the National Health and Nutrition Examination Survey 2005-2006. J Allergy Clin Immun. 2010;126(4);798-806.e13.
While this online article is a synopsis it is misleading regarding the diagnosis and management of food allergy in children.
Food challenges can be extremely dangerous resulting in life threatening anaphylaxis. Food challenges should only be performed by a Board Certified Allergist who is familiar with established protocols. Resuscitative equipment and trained personnel must be present. Food challenges should not be performed by non specialists. The article does not stress the danger of these challenges nor the expertise required to perform them
I AGREE WITH DR. HOWLAND IN THE CASE OF MAJOR ALLERIC REACTIONS SUCH AS PEANUTS BUT FOR THE AVERAGE CHILD WITH CRAMPS AND DIARRHEA, THE SUGGESTIONS OF THA AAP ARE QUITE GOOD AND CLINICALLY WISE I SEE TOO MANY PTS BEING TESTED BUT NO MAJOR CLINICAL GAIN. THE TESTING DFOR MINOR ALLERGIES USUALLY IS NOT DANGEROUS
What is the youngest age for prick skin test?
At what age a child can start having allergy shots?
skin tests are generally recommended at 6 months and above
how ever allergen immunotherapy is usually recommended at 5 years of age unless there have been situations like anaphylaxis to insect sting in which case immunotherapy may be started earlier
The article is good but in my opinion did not go far enough.I agree with Dr Holland wholeheartedly. When skin tests or CAP RAST Tests (In vitro specific IgE levels) are equivocal, a prick test with fresh food followed by a graded challenge with very careful monitoring is mandatory and as Dr Holland commented and is a very serious and potential life-threatening procedure.Regarding the authors comment that “levels of antibodies can help determine whether someone is still allergic” must be taken with caution. Only several foods have been monitored this way and results published-peanuts, milk egg and soy. For others such as tree nuts or shellfish or shrimp there are no such data to my knowledge. The statement regarding the appropriateness of skin testing to antibiotics is not accurate, as we have PrePen available, a reagent which represents the Major determinants for penicillin-a positive prick or intradermal test which is strongly predictive of hives and the Minor determinants-approximated by Penicillin G which is stored for one month-highly predictive of anaphylaxis or serious life-threatening reactions
We thank you all for your instructive commentary and encourage you all to read the original article published in Pediatrics, Jan 2012, which includes more information than this brief excerpt. You can read it at http://pediatrics.aappublications.org/content/early/2011/12/21/peds.2011-2382.full.pdf+html. We look forward to your comments after you have had a chance to read it. Thank you again.
Severe asthmatics should preferably be screened by specificIgE testing. I have seen 2 of my patients go to allergists, get skin testing and develop asthma attack while on preventive medicines.
If the Specific IgE is elevated what additional information do skin tests add?