Data from 175 positive and 30 negative peanut challenges in patients aged 1–26 years were retrospectively correlated with the levels of specific IgE to peanut and peanut components (Ara h 1–3, h 8, and h 9).The best correlation between IgE and clinical thresholds was found for Ara h 2.
A cutoff of Ara h 2 higher than 1.63 kU/l yielded:
- specificity = 1.00
- sensitivity 0.70
Symptom severity elicited during challenge correlated with the levels of Ara h 2, but large individual variation was found.
The level of IgE toward Ara h 2 can improve diagnostic accuracy by introducing a more clear-cut decision-point with an optimal specificity maintaining a high sensitivity. In this study, this would have reduced the necessary number of challenges to be performed from 205 to 92.
Further component-resolved diagnostic cannot replace oral challenge neither in determining thresholds nor in the assessment of severity of symptoms elicited during challenge.
What is a food challenge?
Food challenge is consuming increasing amounts of suspected food at fixed intervals under observation. It is done by feeding gradually increasing doses of the suspected food at 10-30 minutes until a reaction occurs or a normal amount of the food is eaten without causing symptoms. All negative blind challenges end with an open challenge. Oral food challenges are essential to the diagnosis of food allergy.
Oral Food Challenges (click to enlarge the diagram).
References:
Clinical value of component-resolved diagnostics in peanut-allergic patients. E. Eller et al. Allergy, 2012.
Peanut allergy: Diagnostic accuracy of sIgE to Ara h 6 in adults is as good as Ara h 2 http://buff.ly/1uU314i
Image source: Roasted peanuts as snack food, Wikipedia, public domain.
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