Common Allergy Tests Are Not Interchangeable

Data published in Journal of Allergy and Clinical Immunology revealed variations in the results of three common allergy diagnostic blood tests used to quantify sensitivities to allergens. The study, conducted by allergy specialists at Mount Sinai School of Medicine, determined that the laboratory results from two other commercial tests for specific IgE were not equivalent to those measured by ImmunoCAP Specific IgE blood test.

Previously published studies from thought-leading allergists have established threshold values for many food allergens. These values are often used to guide decisions about the severity of a patient's food allergy and subsequent management strategies. These published data are based upon values determined using ImmunoCAP technology, which have become well-established.

"Test results from the three different specific IgE assays are not interchangeable. This study underscores the importance of knowing which test is being used to generate the patient's results, particularly with food allergies, which can be life-threatening," said Robert Reinhardt, MD, professor of family medicine for Michigan State University College of Human Medicine and U.S. Medical Affairs Director, Phadia U.S. Inc.

Specific IgE is produced in the blood as a result of sensitization to an allergen and typically increases with exposure to that substance. High concentrations of food-specific IgE levels are predictive of a food-induced allergic reaction. These ImmunoCAP derived values provide a quantitative assessment of allergen-specific IgE antibody, helping clinicians determine the severity of an allergy and guide patient management strategies.

The assays used in this study included ImmunoCAP, Turbo-MP (Agilent Technologies offered by LabCorp (Laboratory Corporation of America)) and 3gAllergy Universal Module (Siemens' Immulite system). The tests measured specific IgE levels in 50 patients for egg, milk, peanut, cat, birch and dust mite. The results revealed significant differences among the three tests in the measurement of allergen-specific IgE levels, which can impact the clinical decision-making process.

When quantitative evaluation was performed, the Turbo-MP overestimated IgE levels for egg but underestimated levels for dust mite and birch pollen. Differences also were found between Turbo-MP and ImmunoCAP for milk, peanut and cat. The 3gAllergy Universal Module overestimated all allergen-specific IgE levels compared with ImmunoCAP.

"Results from these tests are used to guide treatment decisions, and variability around the decision points can alter clinical management of a suspected allergy," concluded the study authors. "Food allergen avoidance on the basis of inconsistent laboratory results can have profound nutritional and social implications and can significantly affect a child and the child's family's quality of life."

Another study published in the Annals of Allergy, Asthma & Immunology in July 2007 demonstrated that the ImmunoCAP Specific IgE system was directly traceable to the World Health Organization (WHO) standard preparation for total IgE in the detection of quantitative specific IgE antibodies. This traceability to the WHO standard was not equally demonstrated with the Turbo-RAST and 3gAllergy Universal Module specific IgE assays. The study was the first of its kind to compare specific IgE results of different technologies as measured against an independently verified IgE standard.

"These studies further validate ImmunoCAP's overall performance as compared to other specific IgE allergy blood tests, making it a valuable option in the management of allergic disorders," said Michael Land, president and general manager, Phadia U.S. Inc. "Physicians and patients need to be aware that not all allergy blood tests are the same, and here is a study that concludes that interchanging results can put children at unnecessary risk."