ImmunoCAP Specific IgE

ImmunoCAP Specific IgE consists of Complete Allergens (covering over 650 allergens), Allergen Components (covering over 90 components) and Phadiatop, a test designed to differentiate atopic from non-atopic patients.

ImmunoCAP Complete Allergens and ImmunoCAP Allergen Components 
| ImmunoCAP Phadiatop/Phadiatop Infant

Quantifying IgE antibodies with ImmunoCAP Specific IgE accurately evaluates allergy patients. You can learn more about the clinical value, expected test values and test principle of ImmunoCAP Specific IgE here.

Immunodiagnostics offers over 650 different allergens and 90 allergen components for the sensitive and precise quantitative detection of allergen-specific IgE antibodies. IgE antibodies appear in human serum and plasma as a result of sensitization to a specific allergen. Measuring circulating IgE antibodies provides an objective assessment of sensitization to an allergen. In general, low IgE antibody levels indicate a low probability of clinical disease, whereas high levels of antibody to an allergen correlate well with clinical disease.

The clinical value of quantitative testing

For the clinician

  • IgE antibody development can be detected at an early stage, indicating sensitization, even before clinical symptoms have developed
  • Helps explain the allergy march – the progression of allergic disease
  • Helps explain the allergen load – the allergens that together contribute to allergic symptoms
  • Provides clear directions for disease management

For the laboratory

  • Quantitative measuring range from 0.1-100 kUA/l
  • Intra-assay CV (%) comparable with that for routine clinical chemistry immunoassays
  • Excellent consistency over time, and between countries, systems, laboratories and persons

Specimen collection and preparation

  • Serum and plasma (EDTA or heparin) samples from venous or capillary blood can be used
  • Collect blood samples using standard procedures
  • Keep specimens at room temperature (RT) for shipping only
  • Store at 2-8 °C for up to one week, otherwise store at -20 °C
  • Avoid repeated freezing and thawing

Note: Blood samples for testing ImmunoCAP drugs and venom should be collected during or close to the event, and preferably not later than 6 months after exposure. If the test result is negative and an IgE-mediated reaction is still strongly suspected, it is advisable to draw a new sample and repeat the test at 5-6 weeks.

Expected test values 

ImmunoCAP Specific IgE detects IgE antibodies in the range 0-100 kUA /l, where A represents allergen-specific antibodies. The result is reported quantitatively. In clinical practice, 0.35 kUA/l has commonly been used as a cut-off. Numerous studies have evaluated the clinical performance of ImmunoCAP Specific IgE tests in allergy diagnosis. Clinical performance is expressed as sensitivity, ranging from 84-95%, and specificity, ranging from 85-94%. Sensitivity and specificity have been reported from multi-centre studies including several hundred patients tested for a range of allergens.

 

ImmunoCAP Complete Allergens and ImmunoCAP Allergen Components

An allergy diagnosis is based on a detailed case history, clinical observations and results from IgE testing. Using ImmunoCAP Complete Allergens or ImmunoCAP Allergen Components to determine the presence of IgE antibodies offers a broad range of allergens or allergen components to aid the reliable diagnosis of patients with suspected allergy.

  • Knowing IgE antibody levels helps:
  • Tailor advice to individual patients
  • Comply with target allergen exposure reduction
  • Indicate development of tolerance (food allergy, specific immunotherapy)
  • Facilitate optimized individual medical treatment plans (time and dose)
  • Make appropriate referrals

ImmunoCAP Complete Allergens clinical value 

Results from ImmunoCAP Complete Allergens are used to confirm a suspicion of allergy and to determine the offending allergen or rule out allergens for which test results are negative. Results can also be helpful in monitoring IgE antibody levels over time. IgE antibody development can be detected at an early stage, indicating sensitization, even before clinical symptoms have developed, and helping to identify patients at risk of:

  • The allergy march – Progression of skin symptoms to respiratory symptoms
  • Exacerbation – Progression of mild symptoms to severe symptoms
  • Chronicity – Progression of recurrent symptoms to persistent symptoms

ImmunoCAP Allergen Components clinical value

Single allergen components can be produced from an allergen source. Sensitization to these components is then measured individually in separate tests, helping to pinpoint, on a precise molecular level, which component the patient is sensitized to. This information provides the basis for a refined diagnosis of the allergy.

Allergen components are proteins that are grouped into different protein families based on structural similarity. The consequences of being sensitized to members of these families depend on the properties they have in common; they are present in different levels in the sources and have different stabilities. Some allergen components are specific, some are cross-reactive.

What does Molecular Allergology add?

  1. Assess the clinical risk of reaction
    Molecular Allergology enables you to draw conclusions on the risk connected with the sensitization. Sensitization to stable allergen components may elicit both systemic and local reactions, while sensitization to labile components is connected mainly with local reactions.
     
  2. Explain symptoms due to cross-reactivity
    Symptoms elicited by cross-reacting antibodies can be distinguished from those caused by genuine sensitization, which is important for patient management and for giving adequate avoidance advice. In cases where only cross-reactive sensitization is identified, further testing to find the primary sensitizer should be undertaken.
     
  3. Identify the right patients for Specific Immunotherapy
    Sensitization to specific allergen components is essential for successful Specific Immunotherapy. Matching patients having a genuine sensitization with an extract from the relevant source improves treatment outcome.

 

ImmunoCAP Phadiatop/Phadiatop Infant

Determining the presence of IgE antibodies with ImmunoCAP Phadiatop results in appropriate evaluation of atopic patients. You can learn more about the clinical value, expected test values and the test principle of ImmunoCAP Phadiatop/Phadiatop Infant here.

ImmunoCAP Phadiatop is a blood test designed to differentiate atopic from non-atopic patients. Results indicate high or low probability of atopy. A negative result indicates that the symptoms are not caused by common environmental allergens, and the doctor may explore other possibilities.

In younger children aged 0-3, allergic sensitization is mostly related to food allergens (such as egg, milk, fish, soybean and peanut) rather than inhalant allergens. However, antibodies to inhalant allergens such as house dust mites and pets can still appear early in life. With this in mind, a combination of Phadiatop and the most common food allergens is recommended when testing children for atopy.

Clinical value

Phadiatop and Phadiatop Infant are assays for the graded determination of atopy with semiquantitative or qualitative results.  

Semiquantitative results

Phadiatop results are expressed as Phadia Arbitrary Units/l (PAU/l) indicating the degree of sensitization. A Phadiatop PAU/l value above the limit of quantification indicates that the patient is atopic (positive), i.e. measurable levels of specific IgE antibodies to common inhalant allergens have been detected. A Phadiatop PAU/l value below the limit of quantification indicates that the patient is non-atopic (negative), i.e. the level of specific IgE antibodies is undetectable. Higher Phadiatop PAU/l values indicate a higher degree of sensitization, i.e. higher levels of specific IgE antibodies to common inhalant allergens.

Qualitative results

Phadiatop results are expressed as positive or negative. A positive Phadiatop result indicates that the patient is atopic. A negative result indicates that the patient is non-atopic, i.e. not sensitized to inhalant allergens. To determine the concentration of allergen-specific IgE antibodies, it is recommended that the sample be retested with the appropriate ImmunoCAP Specific IgE allergens.

The following clinical results were obtained from clinical trials including 836 patients with suspected allergy:

Final diagnosis
Atopy/non-atopy
 
ImmunoCAP Phadiatop results  
PositiveNegativeTotal
Atopy 483 38 521
Non-atopy 34 281 315
Total 517 319 836

Sensitivity 93%
Specificity 89%

All tests were run using the 0.35 kU/l specific IgE calibrator as cut-off.

Important note

As in all diagnostic testing, a definitive clinical diagnosis should not be based solely on the results of a single test method. A diagnosis should be made by the doctor after the evaluation of all clinical and laboratory findings.