A low-level method for measurement of specific immunoglobulin E antibody in serum

Travis W. Cain, Jan Ford, William K. Dolen

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Background: One of the limitations of serological testing for allergen-specific immunoglobulin E (IgE), compared to skin testing, is the lack of sensitivity. Prior work has suggested that for the Phadia UniCAP System the quantitative cutoff for allergen-specific IgE measurement is set several standard deviations above the assay's lower limit of detection (LLD). Our objective was to examine whether the calibration curve of this assay method preserves its relative linearity at lower levels, and to examine assay background for several arbitrarily selected allergen solid phases. Methods/Data base: To study the total IgE calibration curve, 1:2 dilutions of the 3.5 kUA/L calibration standard were made to an estimated concentration of 0.00625 kUA/L and assayed. Background was measured by assaying system diluent, and a LLD was calculated as the mean background + 3 standard deviations. The background of solid phase ImmunoCAPs specific for oak pollen (t7), timothy grass pollen (g6), short ragweed pollen (w1), cat (e1), peanut (f13), yellow jacket (i3), and penicillin G (c1) was measured, and LLD was calculated. Results: For the total IgE calibration curve, the mean response of the diluent was 15.4 fluorescent units (FU) with a standard deviation (SD) of 2.74, producing an LLD of 23.6 FU and suggesting that the calibration curve ought to be able to measure total IgE levels as low as 0.0125 kU/ L. In contrast, the mean response for the 0.35 kU/L calibrator (the manufacturer's suggested cutoff) was 204 FU (SD 5.21). For the allergen solid phases studied, the mean background responses were t7: 44 (SD 5.02), g6: 22.5 (SD 3.62), w1: 40 (SD 10.6), e1: 26.3 (SD 2.42), f13: 18.3 (SD 1.21), i3: 15.7 (SD 0.52), and c1: 14.3 (SD 1.37) FU respectively. This produced LLDs ranging from 17.2 FU (yellow jacket venom) to 71.6 FU (short ragweed). Conclusion: It appears that this assay system can measure levels of allergen-specific IgE as low as 0.1 kU/L without the need for allergen-specific background controls. The clinical relevance of results in the range of 0.1 0.35 kU/L warrants study.

Original languageEnglish (US)
Pages (from-to)230-233
Number of pages4
JournalAllergy and Clinical Immunology International
Issue number6
StatePublished - Nov 1 2006


  • Allergen-specific IgE
  • Lower limit of detection
  • Serological testing
  • Skin testing

ASJC Scopus subject areas

  • Immunology and Allergy


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