Background: Serum Peanut-specific-IgE (PN-sIgE) and peanut-component-resolved-diagnostics (CRD) are often ordered simultaneously in the evaluation for peanut allergy. Results often guide the plans for peanut oral challenge. However, the clinical utility of CRD at different
total PN-sIgE levels is unclear. A commonly used predefined CRD Ara h2 cutoff value in the literature predicting probability of peanut challenge outcomes is 0.35kUA/L. Objective: To examine the utility of CRD in patients with and without a history of clinical reactivity
to peanut (PN). Methods: This was a retrospective chart review of 196 children with PN-sIgE and CRD testing, of which, 98 patients had a clinical history of an IgE-mediated reaction when exposed to PN and 98 did not. The Fisher's exact test was used to assess the relationship
between CRD and PN-sIgE at different cutoff levels, McNemar test and Gwet’s approach (AC1 statistic) were used to examine agreement between CRD and PN-sIgE, and logistic regression was used to assess differences in the findings between patients with and without reaction history.
Results: Ara h 1, 2, 3, or 9 (ARAH) levels ≤0.35 kUA/L were significantly associated with PN-sIgE levels <2 kUA/L rather than ≥2 kUA/L (p < 0.0001). When the ARAH threshold was increased to 1 kUA/L and 2 kUA/L, these thresholds were still significantly
associated with PN-sIgE levels of <2, <5, and <14 kUA/L. These findings were not significantly different in patients with and without a history of clinical reactivity. Conclusion: ARAH values correlated with PN-sIgE. Regardless of clinical history, ARAH levels
are unlikely to be below 0.35, 1, or 2 kUA/L if the PN-sIgE level is >2 kUA/L. Thus, if possible, practitioners should consider PN-sIgE rather than automatically ordering CRD with PN-sIgE every time. Laboratory procedures that allow automatically and reflexively adding CRD when the PN-sIgE
level is ≤5 kUA/L can be helpful. However, further studies are needed in subjects with challenge-proven PN allergy.
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