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Wise et al.

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Another opportunity offered by tIgE assessment is the ratio between allergen-specific and tIgE. It has been reported that this ratio might be useful in the prediction of AIT effectiveness, 906-908 as recently outlined by the EAACI Position Paper. 909 In summary, tIgE is frequently increased in AR, but the clinical utility is modest in common practice. In fact, the literature is a divergent set of studies that fails to find a consistent role or value for tIgE in the management of AR patients. • Aggregate Grade of Evidence: C (Level 2b: 5 studies; Level 3b: 10 studies; Tables VIII.F.1-1 and VIII.F.1-2). • Benefit: Possibility to suspect allergy in a wide screening. • Harm: Low level does not exclude allergy. • Cost: Modest cost of test. • Benefits-Harm Assessment: Slight preponderance of benefit over harm. In addition, the ratio tIgE/sIgE may be useful. • Value Judgments: The evidence does not support a routine use. • Policy Level: Option. • Intervention: Total IgE assessment is an option to assess atopic status. VIII.F.2. Serum antigen-specific IgE (sIgE)— sIgE testing became commercially available in 1967 with an assay reliant on radioactive anti-IgE for labeling IgE in serum. 910,911 This radioactive technique, known as RAST, has largely been replaced with other technologies using enzymatically-driven reactions to produce a chemiluminescent, colorimetric, or fluorimetric reaction quantified or “read” by an autoanalyzer. 910,912 The process is as follows: allergens are bound to a substrate (typically in the form of a solid or liquid phase) to which a patient’s serum is added. sIgE in the patient’s serum then binds to the allergen on the substrate. Excess serum is washed off and with it, any unbound IgE. Non human anti-IgE antibodies tagged by a marker are subsequently added and bind any corresponding sIgE that is immobilized. Excess anti-IgE antibodies are then washed off and the autoanalyzer reads the intensity of the radioactive, chemiluminescent, colorimetric, or fluorimetric reaction. The intensity of the reaction is proportional to the amount of sIgE in the serum and a report is generated. All tests approved by the FDA are calibrated against a World Health Organization (WHO) tIgE standard serum. 913 Different units are reported depending on the assay system used, but many vendors offer conversion factors. Serum sIgE testing offers several benefits. The safety profile of serum sIgE testing is the best of all available allergy tests as the risk for anaphylaxis is nonexistent. Furthermore, the use of skin testing is limited by the presence of certain medical conditions. In patients where skin testing is contraindicated or potentially impacted by medications or skin conditions, sIgE testing offers a safe and effective option for determining the presence of sensitization as a biomarker of IgE-mediated hypersensitivities and confirming specific allergen triggers.

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Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.