Expected Values

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Note! Good practice recommends that each laboratory establish its own expected range of values.
 
ImmunoCAP gives precise and correct results all through the clinical relevant measuring range. The limit of quantification is equal to the limit of detection, 0.1 kUA/l for 95% of the allergens (1). Dilution curves are parallel to the calibrator, giving the same high recovery independently of IgE antibody concentration and allergen specificity.
 


Fig 1. Limit of quantitation (NCCLS EP17-A) (15) for allergen specific IgE antibodies (internal data 7).

 
In clinical practice, 0.35 kU/l has commonly been used as a cut-off and a large number of studies have been performed in which the clinical performance of ImmunoCAP Specific IgE tests in allergy diagnosis has been evaluated.

Results obtained with samples from healthy blood donors, diseased controls and allergic patients are shown in the figure below. The allergic patients are symptomatic and diagnosed with clinical IgE-mediated allergy. Diseased controls are patients with similar allergy-like symptoms diagnosed as not allergic (2).
 
Fig 2. Healthy non-atopic blood donors (n = 50,data on file).
Allergic Patients (n=527, tests = 3162) are symptomatic and diagnosed with clinical IgE-mediated allergy. Diseased Controls
(n=312, tests = 1792) are patients with similar allergy-like symptoms diagnosed as not allergic (19) (IR19).
 
Interpretation of results

Individual Allergens
IgE Calibrators, traceable via an unbroken chain of calibrations to the 2nd International Reference Preparation 75/502  of Human Serum Immunoglobulin E, are used for the determination of specific IgE antibodies. Values are expressed as kUA/l, where A represents allergen-specific antibodies. Values above limit of quantification represent a progressive increase in the relative concentration of allergen-specific antibodies (3).
 
ImmunoCAP Multiple Allergen
ImmunoCAP Multiple Allergen results are reported as qualitative values (positive or negative). For ImmunoCAP Multiple Allergen 0.35 kU/l is recommended as a cut-off. Values between limit of quantification and 0.35 kU/l may represent very low levels of IgE antibodies. Values > 0.35 kU/l indicate specific IgE antibodies to one or more of the allergens coupled to the ImmunoCAP Multiple Allergen.
 
Reinvestigation with appropriate ImmunoCAP single allergen is recommended when there is a need to further identify and obtain a quantitative result for the specific allergen(s).

A value below 0.35 kUA/l indicates undetectable or very low levels of allergen specific IgE antibodies towards all of the allergens bound to ImmunoCAP multiple allergen but deviations from results obtained with single ImmunoCAP allergens may occur.

The interpretation of results obtained with ImmunoCAP multiple allergen cannot be compared with the results with ImmunoCAP single allergen. The degree of positivity of ImmunoCAP multiple allergen cannot be considered the cumulative degree of positivity of the respective ImmunoCAP single allergen.

References:

    1. ImmunoCAP Specific IgE Directions for Use (Art. No 55-5255-01/03)
    2. Paganelli R et al. Specific IgE antibodies in the diagnosis of atopic disease. Clinical evaluation of a new in vitro test system, UniCAP, in six European allergy clinics. Allergy 1998;53:763-8
    3. Yman L. The new generation of allergy testing. Data on file.