Int J Clin Lab Res 24: 102-105, 1994 9 Springer-Verlag 1994 Comparison of four in vitro assays for specific IgE detection Paola Boccagni, Flavio Favari, Giovanna Zanoni, Angela Pezzini, and Giuseppe Tridente Institute of Immunology and Infectious Diseases, University of Verona, Verona, Italy Summary. Three immunoenzymatic techniques for specific IgE detection (Pharmacia CAP System, Kallestad Allercoat System, Neo Abell6 Hamlet-IgE) and the classical Phadebas RAST were compared using 34 sera from patients with a clinical diagnosis of allergic disease and 19 sera from healthy non-atopic controls. IgE antibodies to 9 aeroallergens and 6 food antigens were assessed and 399 tests were run with each method. All techniques showed a high specificity (92%-100%) and satisfactory efficiency (82%-98%), while the sensitivity for RAST, CAP, Allercoat and Hamlet was 89%, 91%, 83% and 53%, respectively, with the lowest values for food allergens. There was a good overall correlation of the four techniques, except when the Hamlet method was compared with the other methods for food-specific IgE detection (correlation coefficient < 0.3). These data indi- cate that CAP, Allercoat and RAST are satisfactory tech- niques for specific IgE determination, either for inhalants or for food allergens; CAP, however, offers the highest sensitivity without loss of specificity. Key words: Allergy diagnosis - Comparison of immu- noenzymatic assays - RAST - Specific IgE Introduction Allergen-specific serum IgE determination is useful in the diagnosis of atopic diseases. The first in vitro technique for the detection of such antibodies was the radioallergo- sorbent test (RAST), described by Wide et al. [1] in 1967; since then, several, mostly immunoenzymatic, alternative methods have been proposed [2-7]. Sometimes, however, these tests are unsatisfactory with regard to sensitivity, specificity and reproducibility, particularly in the case of food antigens [3-5, 8]. Correspondence to: P. Boccagni, Institute of Immunology and Infec- tious Diseases, Policlinico Borgo Roma, 1-37100 Verona, Italy In this study we compared three immunoenzymatic methods, Pharmacia CAP System (CAP), Kallestad Allercoat Microplate System (Allercoat), Neo Abell6 Hamlet-IgE (Hamlet) and a radioimmunological tech- nique (Pharmacia Phadebas RAST) for the detection of specific IgE to a wide range of both inhalant and food allergens, in order to clarify their diagnostic accuracy. Materials and methods Subjects. We examined sera from 39 adult patients (19 males, 20 females, age range 17-68 years) with allergies to aeroallergens (n = 23) of foods (n = 16). They suffered from: rhinitis (n = 17), rhini- tis and asthma (n=6), dermatitis or urticaria (n= 10), oral allergy syndrome (n=4), gastrointestinal reactions (n= 1) and asthma and dermatitis (n=l). Skin prick tests (SPT) for inhalants were per- formed with Dome Hollister Stier extracts unrelated to those used in in vitro testing, in order to avoid influencing the accuracy of the in vitro techniques; reactions were read after 15 min and graded on a 0 to 4+ scale, as suggested by Eriksson et al. '[9]. The diagnosis was based on clinical history and positivity of SPT for inhalants, while for food allergens clinical findings were confirmed by open and/or double-blind provocation tests; however, only RAST-posi- tire sera were included in the study, as a positive challenge gives no information about the involvement of immunological mechanisms and SPT for food antigens are unreliable [10]. Nineteen pooled sera from healthy adult sex- and age-matched volunteers were used as controls; SPT for the inhalant allergens employed in the in vitro assays were negative. We used pools of sera because of the volume required for testing reactivity to all the allergens with each method. Allergens tested. Serum specific IgE levels were determined by four in vitro assays for the following 9 aeroallergens (dl Dermatopha- goides pteronyssinus, d2 Dermatophagoidesfarinae, el cat epitheli- um, g2 Cynodon dactylon, g5 Lolium perenne, g6 Phleum pratense, gl 3 Holcus lanatus, wl 9 Parietaria officinalis, t3 Betula verrucosa) and 6 food allergens (fl egg white, f3 cod fish, f4 wheat, f8 corn, fl 3 peanut, f49 apple). Patients' sera were tested against the relevant antigens; some subjects reacted with various antigens, so that a total of 114 tests (80 for inhalants and 34 for food allergens) for each technique were performed. Control sera were tested for reactivity with all antigens, giving a total of 285 determinations for each method (171 for inhalants and 114 for food allergens).