Increasing the accuracy of peanut allergy diagnosis by using Ara h 2
The Journal of Allergy and Clinical Immunology March 2012, Vol. 129, No. 3
Thanh D. Dang, BBiomedSc (Hons), Mimi Tang, MBBS, PhD, FRACP, FRCPA, FAAAAI, Sharon Choo, MBBS, FRACP, FRCPA, Paul V. Licciardi, PhD, Jennifer J. Koplin, PhD, Pamela E. Martin, BBiomedSc (Hons), Tina Tan, BSc, Lyle C. Gurrin, PhD, Anne-Louise Ponsonby, BMedSc, MBBS, PhD, FAFPHM, FRACP, Dean Tey, MBBS, FRACP, Marnie Robinson, MBBS, FRACP, Shyamali C. Dharmage, MBBS, MSc, MD, PhD, Katrina J. Allen, BMedSc, MBBS, FRACP, PhD, HealthNuts study
Measurement of whole peanut-specific IgE (sIgE) is often used to confirm sensitization but does not reliably predict allergy. Ara h 2 is the dominant peanut allergen detected in 90% to 100% of patients with peanut allergy and could help improve diagnosis.
We sought to determine whether Ara h 2 testing might improve the accuracy of diagnosing peanut allergy and therefore circumvent the need for an oral food challenge (OFC).
Infants from the population-based HealthNuts study underwent skin prick tests to determine peanut sensitization and subsequently underwent a peanut OFC to confirm allergy status. In a stratified random sample of 200 infants (100 with peanut allergy and 100 with peanut tolerance), whole peanut sIgE and Ara h 2 sIgE levels were quantified by using fluorescence enzyme immunoassay.
By using the previously published 95% positive predictive value of 15 kUA/L for whole peanut sIgE, a corresponding specificity of 98% (95% CI, 93% to 100%) was found in this study cohort. At the equivalent specificity of 98%, the sensitivity of Ara h 2 sIgE is 60% (95% CI, 50% to 70%), correctly identifying 60% of subjects with true peanut allergy compared with only 26% correctly identified by using whole peanut sIgE. We report that when using a combined approach of plasma sIgE testing for whole peanut followed by Ara h 2 for the diagnosis of peanut allergy, the number of OFCs required is reduced by almost two thirds.
Ara h 2 plasma sIgE test levels provide higher diagnostic accuracy than whole peanut plasma sIgE levels and could be considered a new diagnostic tool to distinguish peanut allergy from peanut tolerance, which might reduce the need for an OFC
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