The gold standard for diagnosis of FA is the doubleblind, placebo-controlled OFC. However, in clinical practice the OFC procedure is costly, labour intensive, time and resource consuming, with specialized OFC centres becoming inundated with the increasing number of OFC requests.[3,34] In addition to this, it bears the risk of potential life-threatening anaphylaxis which may discourage patients in pursuing treatments. Therefore, in individuals with suspected PA, SPT and specific immunoglobulin E (IgE) for food allergens are the first-line tests to assess sensitization due to their relatively low cost and rapid results. SPTs and specific IgE have high sensitivity and negative predictive value but have low specificity and low positive predictive value for making an initial diagnosis of FA and therefore may lead to over-diagnosis when used alone.
Among PPs, IgE antibodies to Ara h2, are most often associated with severe allergic reactions. Ara h2 is an important predictor of clinical PA and recent studies have reported that Ara h2-IgE is superior to peanut SPT or sIgE for diagnosis of PA with the best profile of high specificity, high sensitivity and lowest risk of a false-positive diagnosis of PA.[36–41,42] Recently it has been suggested that using s-IgE to Ara h2 as a diagnostic method to differentiate peanut tolerance from PA and reduce the need for OFCs. Although peanut sIgE is more diagnostically sensitive, its low specificity indicates that most patients that test positive in a screening population do not actually have PA. Screening with Ara h 2-sIgE only, instead of peanut s-IgE is more cost-effective, reduces the number of false-positive cases, and reduces the requirement for OFC or referral to an allergic clinic enabling nonspecialists to screen, therefore reducing the time taken to diagnose PA.[37,42,44]
Novel diagnostic tests such as the Basophil activation test (BAT) using whole blood, and the mast cell activation test (MAT) using serum or plasma, are cellular tests that take all components of sIgE into consideration in comparison to quantifying the levels if IgE. Both BAT and MAT have demonstrated high specificity in diagnosing PA,[34,46,47] with BAT showing enhanced sensitivity in comparison to MAT however MAT allowed for deferred testing as it did not require fresh plasma and provided conclusive test results for patients with nonresponding basophils.
The Peanut Bead Based Epitope Assay (Peanut BBEA) measures and compares IgE antibody binding to the levels of two Ara h 2 peanut epitopes to predict the result of the OFC to peanut.[49,50] Compared to the gold standard OFC, the BBEA test is more effective and efficient. It has an accuracy of 93% for diagnosing PA, greater than the accuracy of SPT and s-IgE, combined with a two to nine-fold reduction in false-positive rate than other diagnostic tests. Ongoing studies suggest that BBEA assay may capable of indicating what dose of PP may initiate an allergic reaction however further research in this area is needed.[52,53] This low-risk diagnostic test requires small quantities of plasma or serum, is easily adaptable to the standard clinical lab due to its reproducibility and performance and has the potential to reduce the need for OFC.[51,54]
Curr Opin Allergy Clin Immunol. 2022;22(3):188-193. © 2022 Lippincott Williams & Wilkins