Study Points to Predictors of Egg Allergy Resolution

SAN ANTONIO, Texas — In babies allergic to eggs, the most significant predictor of allergy resolution within 3 years is baseline egg-specific immunoglobulin E (IgE) level, according to a subanalysis of a Consortium of Food Allergy Research (COFAR) study.

The information is important for parents and can also help guide clinical decisions, lead investigator Scott Sicherer, MD, told Medscape Medical News. "If you have a patient in front of you with these parameters suggesting they're likely to outgrow this allergy in 3 years, why would you put them through a whole bunch of treatments like immunotherapy, for example?"

The observational study, which Dr. Sicherer presented as a featured poster here at the American Academy of Allergy, Asthma & Immunology (AAAAI) 2013 Annual Meeting, included 209 children fulfilling clinical and laboratory criteria for egg allergy.

During a median follow-up period of 71 months, 44% of patients experienced a resolution of their allergy. This was defined as ingestion of egg without symptoms with a median age at resolution of 69 months.

"This was pretty typical for an allergy office referral population," said Dr. Sicherer. "If you're in a pediatric practice looking at children with egg allergy, that's different than in an allergy practice where the worst cases will come."

The investigators found that allergy resolution was significantly associated with baseline IgE level. Patients with persistent allergy had a median level of 6.2 kU/L compared with a median of 1.8 kU/L in patients whose allergy resolved.

The less significant predictors included baseline skin-prick wheal size, immunoglobulin G4 (IgG4) level, and severity of atopic dermatitis.

Table. Egg Allergy Resolution During the 3-Year Study Period

Baseline Variable	Persistent Allergy n = 118 (%)	Allergy Resolved n =9 1 (%)	P-Value
Egg IgE < 2 kU/L	40	60	< .001
Egg IgE 2 - 10 kU/L	57	43	< .001
Egg IgE > 10 kU/L	78	42	< .001
Wheal size < 5 mm	43	57	= .001
Wheal size 5 - 10 mm	67	33	= .001
Wheal size > 10 mm	53	47	= .001
IgG4 < 0.1 mg/L	47	53	= .027
IgG4 – 0.4 mg/L	57	43	= .027
IgG4 > 0.4 mg/L	69	31	= .027
No or mild atopic dermatitis	45	55	= .041
Moderate or severe atopic dermatitis	62	38	= .041

"If the level was 10 kU/L, there was only a 22% chance of outgrowing the allergy in this time period, but if the level was 2 kU/L, there was a 60% chance," said Dr. Sicherer.

Compared with patients with IgG4 levels greater than 4 mg/L, those with levels between 0.1 and 0.4 mg/L were more likely to have their allergy resolve (hazard ratio [HR], 1.5). Patients with levels lower than 0.1 mg/L were even more likely to be able to eat eggs (HR, 2.1; P = .027).

Similarly, compared with patients with skin-prick wheals measuring more than 5 mm, those with wheals less than 5 mm were likely to have their allergy resolve (HR, 1.9; P = .001).

Patients who had moderate to severe atopic dermatitis were more likely to be allergic, whereas patients with no dermatitis or with a mild case were likely to have their allergy resolve (HR, 1.7; P = .041).

However, in multivariate analysis adjusting for baseline egg-specific IgE, these other predictors lost their statistical significance.

Outgrowing Egg Allergy

"So overall, it would be bad news if your patient had really bad eczema, a really big skin test, and really high IgE because they're going to have a slower outgrowing course," said Dr. Sicherer.

But he emphasized the study period was very short. "It only goes to 71 months, and studies still say most kids do outgrow egg allergy by the time they're adolescents — although maybe not as fast as before. So while a slower prognosis is bad news for families, most kids do eventually outgrow their egg allergy."

Asked to comment on the findings, Dr. Stuart Abramson, MD, head of the AAAAI scientific program committee and staff allergist and immunologist at Shannon Medical Center in San Angelo, Texas, told Medscape Medical News, "We're always looking to figure out who's going to outgrow the allergy. This group found that baseline level of egg-specific allergen was a very important predictive factor, and having an objective measure like that is important. If someone has a number below this threshold that they've identified, that's an important bit of information and alleviates some anxiety, and just because they have a higher level doesn't mean they won't outgrow it necessarily, but they're at a higher risk."

Dr. Sicherer's group recently published similar predictors for milk allergy ( J Allergy Clin Immunol 2013;131:805-812), and COFAR has an online Milk Allergy Resolution Calculator to help physicians counsel families about the likelihood of allergy resolution. Dr. Sicherer says the plan is to post a similar calculator for egg allergy.

This study is funded by the National Institutes of Allergy and Infectious Disease. Dr. Sicherer has received grants from the study sponsor and works as a consultant for the Food Allergy Initiative. Dr. Abramson has reported no relevant financial relationships.

American Academy of Allergy, Asthma & Immunology (AAAAI) 2013 Annual Meeting. Abstract 509. Presented February 24, 2013.