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Frequently Asked Questions

Product Detail | Interpretation of Results | Implementation | Cost/Billing | Miscellaneous

Product Detail

Why do allergy specialists test for many more allergens than the Upper Respiratory Disease Profile?

Some physicians consider extensive diagnostic testing for patients who are being considered for immunotherapy treatment.

The use of a quantitative mini-panel, such as the Upper Respiratory Disease Profile, consisting of a least 1 highly prevalent representative of each major inhalant allergen group (6 to 10 total), was shown to detect more than 95% of patients with atopic conditions. (Pharmacia Diagnostics Atopic Factors in Upper Respiratory Disease, 2000)

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Are all in vitro tests for allergy reliable?

In vitro testing has evolved through many generations, and today's ImmunoCAP® technology is much more accurate than previous testing (ie, RAST). A recent study in the Journal of Allergy and Clinical Immunology (June 2000) by P. Brock Williams and colleagues found that ImmunoCAP outperformed all other specific IgE lab tests and produced assessments that approached the standard of an ideal assay. This state-of-the-art system is capable of measuring specific IgE antibodies with precision and accuracy, and it is at least as good as skin testing. In recent studies looking at clinical efficiency (taking sensitivity and specificity into account), ImmunoCAP results were equal to skin prick testing and significantly better than intradermal testing. (JACI, June 2000, Yunginger, et al; JACI, May 1999, Wood, et al)

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Interpretation of Results

For what type of patient symptoms would I order the test?

Patients suspected of having an IgE-mediated disease such as allergic rhinitis and co-morbid conditions. Investigators have noted an association between allergic rhinitis and asthma, sinusitis, otitis media, recurrent respiratory infection, and, possibly, nasal polyposis. (Impact of Allergic Rhinitis and Related Airway Disorders, Baraniuk, et al, 1996, 99080.RPC 1)

Do levels of results correlate to increased severity of symptoms?

Interpretation: The higher the response value, the more specific IgE is present in the sample. A high or low specific IgE level may not necessarily correlate to the degree of symptom severity, as each person's symptomatic threshold varies.

In different patients and on different occasions, the relationship between sensitization, inflammation, and hyperresponsiveness may be substantially different, leading to very heterogeneous patterns of clinical symptoms. Infections and treatment may also influence the sensitization process and the presence of symptoms. (Mediators in Allergy Diagnosis, Ahlstedt, S., 98063.RP)

A definitive clinical diagnosis should not be based on the results of any single diagnostic method, but should be made by the physician only after all clinical and laboratory findings have been evaluated.

How should I interpret kU_A/L results for inhalants?

Sample Patient Report

Implementation

How much blood is needed for testing?

40 microliters + dead volume per allergen is needed (1 serum separator tube or red top for a panel of allergens). EDTA plasma may also be used (UniCAP Specific IgE Procedure).

50 microliters + dead volume per allergen is needed for Pharmacia CAP System™ or AutoCAP™.

* Please contact your laboratory to determine the exact quantity of sample they require per test.

At what age can a patient be tested?

Increased environmental allergen exposure, combined with the proper genetic constitution, may cause increased prevalence of allergic diseases. Foods may be more important to start sensitization early in life. The earliest predictor for development of allergic disease seems to be IgE antibodies specific to hen's egg white. Such antibodies were recently found at 6 months of age to precede further IgE antibody formation at 5 years of age to inhalant allergens, such as mite allergen. They indicate the development of an atopic constitution, with specific IgE antibody formation to food allergens in the very young child and to inhalant allergens later in life. (Mediators in Allergy Diagnosis, Alhstedt. S., 1998, 98063RP)

How do ImmunoCAP test results compare to skin testing?

Summary: A May 1999 study done by Dr. Wood and associates at Johns Hopkins University School of Medicine revealed that ImmunoCAP testing exhibited excellent diagnostic efficiency when compared to skin prick testing. Intradermal skin testing added little to the diagnostic evaluation of allergy.

Annals of Allergy, Asthma, and Immunology; May 1999

Journal of Allergy and Clinical Immunology, Vol. 96, No. 5, Part 1, November 1995

A Comparison of Skin Prick Tests, Intradermal Skin Tests, and RASTs in the Diagnosis of Cat Allergy

Robert A. Wood, MD; Wanda Phipatanakul, MD; Robert G. Hamilton, PhD; and Peyton A. Eggleston, MD

Journal of Allergy and Clinical Immunology, Vol. 103, No. 9, Part 1, May 1999

The Study
One-hundred twenty patients were challenged with a cat exposure model after first evaluating by history, skin prick tests (SPTs), intradermal skin tests (IDSTs) if SPT results were negative, and in vitro allergy testing using Pharmacia & Upjohn technology. Purpose of the study was to determine the predictive value of SPTs, IDSTs, and RASTs.

Conclusion
"Although both SPT and RAST values exhibited excellent efficiency in the diagnosis of cat allergy, IDST scores added little to the diagnostic evaluation." (pp. 773-779)

Editorial Highlights

• SPTs and RASTs exhibited high levels of sensitivity, specificity, positive predictive values (PPVs), negative predictive values (NPVs), and overall efficiency. (p. 777)
• The poor sensitivity, poor specificity, and positive predictive efficiency of IDSTs suggest they be used with caution and never be used alone as the basis for major therapeutic decisions.
• For respiratory allergy, no gold standard for testing exists, although the authors suggest well-standardized and highly potent SPT as the most sensitive.
• It is noted that potency of allergen extracts can result in variations in SPT results. Further, test methods used in the application of SPTs can vary, and it is imperative that clinicians select a method that has been adequately tested and standardized. (p. 779)
• RAST displayed excellent sensitivity, specificity, PPVs, and NPVs.
• RAST scores were indicated as somewhat less sensitive than SPT, although it was noted that sensitivity would have been improved had ImmunoCAP been used throughout the study.
• While the authors acknowledge this study was based on cat allergen only, the expectation is that results would be similar across most, if not all, allergens. (p. 779)

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Studies on the Relationship Between the Level of Specific IgE Antibodies and the Clinical Expression of Allergy: Definition of Levels Distinguishing Patients With Symptomatic From Patients With Asymptomatic Allergy to Common Aeroallergens

Journal of Allergy and Clinical Immunology, Vol. 96, No. 5, Part 1, November 1995

The Study and Its Purpose
The American Academy of Allergy, Asthma, and Immunology identified a need for a quantitative assay to "facilitate better definition of the relationship between quantity of IgE antibody and the symptoms or risk of disease." This study was designed to determine whether, in patients with some evidence of allergy, results from in vivo tests and quantitative results from in vitro tests would allow clinicians to distinguish those patients with clinically significant allergic disease from those with no clinical symptoms.

Summary of Results/Conclusions

• Sensitivity, specificity, and diagnostic values for the antibody assays were determined and compared with values obtained similarly for skin prick test (SPT) results.
• Skin testing had a lower diagnostic value (sum of sensitivity and specificity) than the Pharmacia CAP System™ (ImmunoCAP Technology) in vitro test.
• The cutoff values for ImmunoCAP appear to be more useful than the cutoff values for SPT, because they have a greater diagnostic value (the sum of sensitivity and specificity).
• It was concluded that the cutoff values for specific serum IgE antibody levels are likely to be useful in clinical practice to distinguish symptomatic from asymptomatic allergy in patients with positive skin test results.

Do patients need to be off medications (ie, steroids, antihistamines, chromolyn sodium, etc) for testing?

The ImmunoCAP Specific IgE Bood Test quantitatively measures immunoglobulin E. The test is not influenced by medications such as anti-histamines, steroids, or chromolyn sodium.

Cost/Billing

Will the cost of performing the test exceed the cost of the antihistamine use?

An average of 2.9 prescriptions for nonsedating antihistamines is filled per patient per year. (Drug Topics Redbook, March 2000). If the average cost of a prescription is $60 to $90, the patient may spend between $174 and $261. If the patient is proven to have negative specific IgE test results, the cost of the NSAs may be avoided.

Miscellaneous

Who should be tested?

While anyone presenting with nasal or other allergy-like symptoms is a candidate for specific IgE testing, it is not likely that everyone with a runny nose needs the test. ImmunoCAP® Specific IgE Blood Test should be strongly considered for patients with:

• recurrent or chronic Upper Respiratory Disease (URD), ie, rhinitis, sinusitis, allergic rhinitis
• unseasonal allergy-like symptoms
• seasonal or perennial allergy-like symptoms
• recurrent otitis media

• Current Issues Relating to In Vitro Testing for Allergen-specific IgE: A Workshop Report
• Impact of Allergic Rhinitis and Related Airway Disorders
• Quality of Life in Asthma: Internal Consistency and Validity of the SF-36 Questionnaire

What do allergy specialists think of the ImmunoCAP test?

Summary: A panel of experts in the area of allergy diagnosis met in 1997 and concluded that the panel supported the use of well-standardized in vitro tests as an alternative to the use of skin testing. The workshop panel also supported selective use of in vitro testing by generalist physicians to effectively manage and properly refer patients to allergists for specialist care. (15th Annual Aspen Allergy Conference, reported in Current Issues, May 1999, 99067.RPC1)

Current Issues Relating to In Vitro Testing for Allergen-specific IgE: A Workshop Report

Annals of Allergy, Asthma, and Immunology; May 1999

Purpose of Workshop
To discuss the current status of in vitro testing for allergen-specific IgE and to examine various applications of this technology in routine clinical practice. Workshop panelists consisted of a distinguished group of physicians and scientists and known thought leaders in the areas of allergy and immunology. Members of this auspicious group have published 792 articles in this field.

Use of IgE in Clinical Practice

• Patient history is not enough for specific allergen identification, which is necessary for appropriate treatment.
• Well-standardized in vitro tests are an alternative to skin testing, and there are special situations where in vitro testing may be preferable or specifically indicated.
• Every physician who is seeing a suspected allergic patient should consider testing for allergen-specific IgE to identify the specific cause.
• In vitro testing by generalist physicians (family practitioners, internists, pediatricians) is appropriate to effectively manage and properly refer patients. They suggest initial screening with a basic panel based on patient history.
• In Vitro (Blood) Testing vs. Skin Testing
• NIH guidelines for asthma recommend either in vivo or in vitro to identify specific allergen sensitivities.
• "Compared with skin testing, in vitro testing may be easier to standardize, and performance characteristics can be defined."

• Results from proficiency testing surveys suggest that not all in vitro tests for IgE perform equally well; further, they acknowledged that in vitro technology has significantly advanced since its inception.
• Specific IgE Assay Calibrators should be standardized against the WHO Reference Preparation for IgE for true quantitative results.

Health Care Providers: Which laboratories in my area offer ImmunoCAP Specific IgE testing?

Patients or parents of patients: Which physicians in my area offer ImmunoCAP testing?

Please contact a clinical specialist toll-free at 877-862-4948 for additional information.