Comparability and quality of IgE-based in vitro allergy diagnosis: 25 years of external quality assessment.

A large variety of methods and a wide range of products from several manufacturers are available for IgE-based in vitro allergy testing. In the large majority of cases, the attending physician lacks information about the devices and products used in the laboratory performing the tests. To determine the comparability and reliability of different laboratories, we analyzed the findings of an international ring trial established in Austria 25 years ago.The results were satisfactory: 97.4 % of total IgE tests and 93.9 % of antigen-specific IgE tests were correct. Further analysis revealed more false-positive than false-negative antigen-specific IgE levels (17.1 vs. 5.2 %). The investigation of different allergen groups yielded excellent results for some allergens (97.8 % correct values for mites, or 99.6 % correct values for recombinant antigens), but quite unfavorable for others (21.4 % incorrect values for drugs). In view of this paucity of comparability and reliability, it would be appropriate to establish mandatory quality control in laboratories and manufacturing units.