Food, drug, insect sting allergy, and anaphylaxis
Correlation of serum allergy (IgE) tests performed by different assay systems

https://doi.org/10.1016/j.jaci.2007.12.1150Get rights and content

Background

In vitro testing is commonly used to diagnose and manage allergies. Clinical reactivity has been correlated with food-specific IgE levels by using the ImmunoCAP (Phadia, Uppsala, Sweden).

Objective

To determine whether IgE levels derived from different assays are equivalent to those measured by ImmunoCAP.

Methods

Fifty patients from the Mount Sinai Pediatric Allergy practice were prospectively enrolled. For each deidentified sample, specific IgE levels were measured to egg, milk, peanut, cat, birch, and Dermatophagoides farinae at different laboratories, each using a different assay system (Phadia ImmunoCAP, Agilent Turbo-MP, and Siemens Immulite 2000). Results were analyzed to determine whether IgE measurements were equivalent. Food allergen–specific IgE levels were correlated with clinical data and around empirically determined thresholds that predict probability of clinical disease in 50% or 95% of subjects.

Results

Variable degrees of agreement existed among the 3 assays. Immulite 2000 overestimated all specific IgE levels compared with ImmunoCAP. Turbo-MP overestimated for egg but underestimated for birch and D farinae. Differences for milk, peanut, and cat were observed, without a trend toward overestimation or underestimation. Furthermore, several values for the food allergens were discrepant around the 50% and 95% positive predictive values for clinical reactivity.

Conclusion

Discrepancies in specific IgE values from 3 different assays can potentially lead to altered management and treatment. The predictive values for clinical reactivity associated with food-specific IgE levels determined by ImmunoCAP should not be applied to results from other assays.

Section snippets

Patients

Infants/children and adolescents from 6 months to 21 years of age who were evaluated at the Mount Sinai Pediatric Allergy and Immunology practice and who had blood drawn for routine management were eligible to participate in this study. The patient history and physical examination, skin prick tests, and blood tests for allergen specific IgE levels were performed as part of standard clinical care. Written informed consent was obtained before enrollment. An additional blood sample (15 mL) was

Patients

Fifty consecutive patients who consented to participation were enrolled. The median age of the participants was 7.25 years (range, 2.92-18 years). Thirty-three were male and 17 were female. This was a highly atopic population with 42 diagnosed with food hypersensitivities (5 other patients avoided specific foods because of a history of positive skin prick tests or serum-specific IgE levels, and 3 patients had no history of food hypersensitivity), 42 with allergic rhinitis, 30 with atopic

Discussion

Measurement of allergen-specific IgE levels is important in the diagnosis of clinical allergy as well as the management of individual patients. We compared IgE levels measured by ImmunoCAP, our reference standard, with those measured by Immulite and Turbo-MP. Consistent with previous studies,6, 7, 8, 9 our data demonstrate significant differences in the measurement of IgE levels in identical serum samples using these 3 commercial assay systems. In our study, allergen-specific IgE levels

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All costs for the laboratory analysis were covered by Phadia AD, Uppsala, Sweden.

Disclosure of potential conflict of interest: J. Wang has received research support from Phadia. H. A. Sampson has consulting arrangements with Allertein and has received research support from Phadia and the National Institutes of Health. J. H. Godbold has declared that he has no conflict of interest.

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