Allergen-Specific IgE on IMMULITE^® 2000: A "Third Generation" Allergy Blood Test

The past two decades have witnessed significant technological advances in the realm of in vitro allergy testing. The original first generation* in vitro assays for allergy diagnosis were isotopic assays requiring overnight incubations. The first generation assays were arbitrarily calibrated and utilized solid-phase allergens linked by cyanogen bromide chemistries. One significant problem with these first generation assays was increased nonspecific binding, often due to inefficient washing of the tracer from solid-phase allergens.

As technology advanced, nonisotopic second generation* assays were introduced, which utilized enzyme substrates and fluorescence for detection of specific IgE. The second generation assays, performed mainly on batch processors, were easier to use and featured detection limits of 0.35 kU/L.³ These assays represented a significant technological improvement over the first generation assays, with a time-to-first-result of hours rather than days.

The introduction of allergen-specific IgE testing on the IMMULITE^® 2000 has advanced in vitro allergy testing to a new level of precision, analytical sensitivity, functional sensitivity and convenience.^4,5 Classified as a "third generation" allergy blood test for specific IgE determination, allergy on IMMULITE 2000 combines improvements in sensitivity with full random access automation. The use of liquid allergens allows for complete automation capability with a time-to-first-result of 65 minutes. Enzyme-enhanced chemiluminescence technology used in specific-IgE measurement on the IMMULITE 2000 allows for a functional sensitivity of 0.2 kU/L and a lower detection limit of 0.1 kU/L. The assay also demonstrates linearity under dilution down to the limit of 0.1 kU/L, with dilution factors ranging from 1 to 1000 rather than 1 to 100 as with second generation FEIAs. Allergy testing on the IMMULITE 2000 features an extensive menu, which currently includes 245 allergens and 35 allergen panels. "Third generation" allergy testing on the IMMULITE 2000 enables any clinical laboratory to consolidate workstations and transform allergy blood testing into a routine, cost-effective offering.

* The "generational" characterization of allergen-specific IgE assays is widespread in the literature. See, for example, Plebani et al.¹ and Hamilton et al.²

References
1. Plebani M, Bernardi D, Basso D, Borghesan F, Faggian D. Measurement of specific immunoglobulin E: intermethod comparison and standardization. Clin Chem. 1998 Sep;44(9):1974-9.

2. Hamilton RG, Adkinson NF Jr. Clinical laboratory assessment of IgE-dependent hypersensitivity. J Allergy Clin Immunol. 2003 Feb;111(2 Suppl):S687-701.

3. Yunginger JW, Ahlstedt S, Eggleston PA, Homburger HA, Nelson HS, Ownby DR, Platts-Mills TA, Sampson HA, Sicherer SH, Weinstein AM, Williams PB, Wood RA, Zeiger RS. Quantitative IgE antibody assays in allergic diseases. J Allergy Clin Immunol. 2000 Jun;105(6 Pt 1):1077-84.

4. Tse S, Chuang T, Li TM, Hovanec-Burns D, El Shami AS. Analytical performance evaluation of the allergen-specific IgE assays on the IMMULITE^® 2000 system. Allergy 2003: 58 (Suppl 74):364.

5. Li TM, Chuang T, Tse S, Hovanec-Burns D, El Shami AS. Development of a third generation allergen-specific IgE assay on the continuous random access IMMULITE^® 2000 analyzer. Clin Chem 2003;49(S6):A20.