3gAllergy™
News from the EAACI

DPC's third-generation allergen-specific IgE assay for use with DPC's IMMULITE^® 2000 and IMMULITE^® 2500 immunoassay platforms is becoming more widely recognized and trusted for allergy testing by laboratories throughout the world. This methodology was launched in Strasbourg, France in 2001, and subsequently featured at various scientific meetings, including the annual meeting of the American Academy of Allergy, Asthma and Immunology (AAAAI) last March. However, DPC's allergen-specific IgE assay made its official European debut under its brand name of 3gAllergy™ at the congress of the European Academy of Allergology and Clinical Immunology (EAACI) held in Amsterdam this past June. Many of the congress attendees visited the DPC booth and received information on 3gAllergy and the investigation of allergen crossreactivities.

3gAllergy and early diagnosis of allergic diseases
DPC is committed to educating physicians about 3gAllergy as a tool to help them diagnose, and therefore treat, their youngest patients earlier than was previously possible. Early measures (allergen avoidance, pharmacotherapy and treatment) are key to preventing the progression of allergic diseases. With its exceptional sensitivity, 3gAllergy can help identify sensitized children sooner by detecting specific IgE below the traditional cutoff of 0.35 kU/L. A new brochure for physicians, describing allergy testing guidelines and the benefits of 3gAllergy, was provided at the EAACI congress booth.

Investigation of allergen crossreactivities
Crossreactivity between allergens sharing homologous molecular sequences is a frequent problem that can affect the clinical diagnosis. The identification of such reactions when they happen is therefore critical for the physician. Different in vitro procedures such as inhibition tests and immunoblotting inhibition are well-established methods of investigation, enhancing the specificity of the in vitro result when an allergen crossreaction is suspected. DPC offers a full package of information including in vitro procedures, a poster and a CD-ROM about investigating in vitro allergen crossreactivity.

New data on 3gAllergy from France and Germany
3gAllergy figured in several posters and in an oral presentation during the congress. Dr. L. Guilloux (Lyon, France) investigated the performance of nine major 3gAllergy food allergens (including egg white, milk and milk proteins, fish, wheat, peanut and mustard) and compared them to the corresponding allergens of the Pharmacia CAP system.

She observed very good agreement between the two systems for the quantitative measurement of food-specific IgE. She also investigated discrepant peanut allergen results. The CAP system demonstrated a higher reaction with crossreacting carbohydrate determinants (CCDs) for the peanut allergen than did the IMMULITE 2000. This crossreaction with CCDs leads to a higher quantification of peanut-specific IgE in the CAP system and to false-positive in vitro results relative to the patient's clinical history. In routine practice, positive in vitro results for peanut allergen may lead to unnecessary avoidance diets, in the absence of confirmation by clinical examination of the patient.

Dr. B. Wedi (Hannover, Germany) reported on an analytical performance study of the IMMULITE 2000 and Phamacia CAP systems for total IgE and specific IgE on 18 individual allergens and a comparison of the two systems with clinical history and skin test results. The objective was to evaluate the performance of the IMMULITE 2000, a fully automated immunoanalyzer which employs enhanced chemiluminescence and liquid allergens, against the performance of the widely used Pharmacia CAP system, which employs allergens coupled to a solid matrix.

The correlation between interassay and intraassay results for the IMMULITE 2000 was high (R = 0.997 to 1.0). Correlation with the CAP system was very good for total IgE (R = 0.991). Total agreement was 62.3% (all classes) for both systems with respect to all 18 allergens. Compared to clinical history and skin test results, however, significant differences were observed in the diagnostic performance of both systems for cultivated rye grass, mugwort, D. pteronyssinus, egg white, wheat, soybean, peanut and bee venom. The authors found that although both systems show good agreement, the results obtained for individual allergens by the two systems can differ from clinical history and skin tests results. On the basis of this study, they concluded that there is no longer justification to consider one system as the "gold standard."

DPC posters
In addition, DPC presented two of its own posters at the EAACI congress.

Quantification of allergen-specific IgE (sIgE): Comparison of logistic regression-derived probability curves obtained from two quantitative sIgE methodologies—Pharmacia CAP FEIA and DPC IMMULITE^® 2000

The authors showed that the IMMULITE 2000 and Pharmacia CAP systems yielded comparable probability curves for the inhalant and food allergens tested. The IMMULITE 2000 system, however, provides precise quantification down to 0.2 kU/L, which permits extending probability curves below 0.35 kU/L. Thus, it can assess assay performance more definitively at the traditional 0.35 kU/L cutoff and is a better tool for defining probability curves.

The poster's conclusions are important because significant IgE-mediated allergic symptoms can be present even at low levels of allergen-specific IgE.

Establishing DPC QualityNet—A Novel External Quality Assurance Program in Germany for Monitoring Laboratory Performance of the Third-Generation Allergen-Specific IgE and Total IgE Assays on the IMMULITE^® 2000 System

This poster reported on preliminary results of DPC's newly developed quality assessment program for IMMULITE 2000 users in Germany. Several external QC surveys are based on pretreated, stabilized sample material; the outcome of such surveys may not reflect the typical daily performance of the laboratory. The DPC QualityNet QC program is based on fresh-frozen native serum samples drawn from individual patients with well-documented allergic clinical histories. Results for several lots of individual allergens from 43 laboratories had interlaboratory CVs of 9.5 to 15.1%. Of the participating laboratories, 92 to 100% fulfilled the criteria of the German INSTAND proficiency survey for specific IgE. These results demonstrate the IMMULITE 2000 system's excellent performance under routine laboratory conditions.

DPC thanks the customers and their referring physicians who visited the DPC booth during the EAACI congress. For more information, please contact your local DPC representative.

The DPC posters are available at DPC's website—www.dpcweb.com—under Technical Documents, Scientific Posters, 2004 European Academy of Allergology and Clinical Immunology.