Objectives: In this study, we compared 2 different immunoassays, HY*TEC enzyme immunoassay (Hycor Biomedical Inc, Garden Grove, CA) and Pharmacia Upjohn ImmunoCAP (Pharmacia and Upjohn, Kalamazoo, MI) using skin end-point titration as a gold standard by receiver operating characteristic analysis.
Materials: One hundred patients were enrolled in this study and were tested with the above 3 modalities. The results were analyzed by receiver operating characteristic analysis, in which the curves give a decision criterion for any diagnostic test relative to its sensitivity and specificity against an accepted gold standard test. Only inhalant allergens (Dermatophagoides pteronyssinus, Dermatophagoides farina, cat dander, giant ragweed, English plantain weed, timothy grass, Alternaria tenuis, Aspergillus fumigatus, meadow fescue, oak tree, white ash tree, and lamb's-quarter weed) were studied.
Results: The results obtained with both ImmunoCAP and HY*TEC showed a good correlation with skin end-point titration for D pteronyssinus, D farina, cat dander, giant ragweed, timothy grass, A tenuis, and meadow fescue, with sensitivities ranging from 71% to 88%. However, the sensitivity of both tests to English plantain weed, lamb's-quarter weed, oak tree, and white ash tree was lower (66% down to 39%). Additionally, HY*TEC results were not satisfactory for detecting specific IgE to A fumigatus (30% sensitivity). The overall sensitivity for each test was 65.67% for the HY*TEC and 71.25% for the ImmunoCAP.
Conclusion: The 2 in vitro testing systems are comparable for most of the allergens, except for A fumigatus, English plantain, lamb's-quarter, and white ash tree; ImmunoCAP and HY*TEC would benefit from improved technology for detecting these specific IgE antibodies. The HY*TEC assay did not give acceptable results for A fumigatus. The overall assay characteristics were good to excellent for each system tested.