Relationship between the outcome of low-dose egg oral immunotherapy and the fold-difference levels of allergen-specific IgE and IgG4 in serum.

Background: There are no indices to monitor desensitization by low-dose egg oral immunotherapy (eOIT).

Objective: We aimed to examine the relationship between desensitization by low-dose eOIT and the changes in allergen-specific immunoglobulin E (IgE) and IgG4 levels.

Methods: We carried out low-dose eOIT in 31 patients with severe egg allergy in our previous two studies. After 4 months of treatment, the patients with no observed allergic symptoms in response to the open hard-boiled egg white challenge tests were classified as the negative group, and the remaining patients, the positive group. The fold-difference levels were calculated using 10 Log (Titer after eOIT/Titer before eOIT).

Results: The 28 patients who completed eOIT with sufficient serum collected before and after eOIT were analyzed. The median fold-difference levels of ovomucoid-specific IgE in the negative and positive groups were 0.819 and 0.953, respectively (P = 0.082). The median fold-difference levels of ovalbumin-specific IgG4 in the negative and positive groups were 2.01 and 1.29, respectively (P = 0.057). In the receiver-operating characteristic curves, the area under the curves of fold-difference ovomucoid-specific IgE and ovalbumin-specific IgG4 were 0.701 and 0.719, respectively. The challenge positive predictive values of fold-difference ovomucoid-specific IgE and ovalbumin-specific IgG4 were 83.8% (cut-off point: 0.934) and 77.8% (cut-off point: 1.87), respectively. Moreover, the challenge positive predictive value in patients with both 0.934 < ovomucoid-specific IgE and ovalbumin-specific IgG4 <1.87 was 100%.

Conclusions: The fold-difference levels of allergen-specific IgE and IgG4 in serum are considered useful for monitoring desensitization by low-dose OIT.