Comparison between MAGIC LITE®‐ and CAP®‐system: two automated specific IgE antibody assays

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Abstract
The MAGIC LITE system, a newly developed immunochemiluminometric assay for specific and total IgE antibody using paramagnetic particles coupled with standardized allergens as solid phase, was compared to the CAP system, a recently introduced immunoassay based on a cellulose polymer encased in a capsule. A total of 357 serum samples of patients with suspected inhalant allergies and a positive skin prick test (SPT) to common allergens (birch, timothy‐grass, mugwort, cat dander, Dermatophagoides pteronyssinus, Alternaria) were investigated. Fifty SPT negative subjects served as controls (total number of tests in each assays = 1600). Both assays were highly precise (overall intra‐assay and inter‐assay coefficients of variation were 2.9% and 4.5% in MAGIC LITE, 4.7% and 5.5% in CAP) and showed excellent linearity (mean r2 of eightfold log2 serum dilutions were 99.7% and 99.3% in MAGIC LITE and CAP). Good correlations were found between the absolute specific IgE antibody values detected by both methods (correlation coefficient r: birth 0.86, grass 0.93, mugwort 0.96, cat 0.91, D. pteronyssinus 0.73, Alternaria 0.90). Excellent specificity (.98%) occurred in both assays and with all allergens, and sensitivity was related to the allergen (MAGIC LITE/CAP): birch 91%/89%, grass 83%/90%, mugwort 50%/69%, cat 83%/83%, D. pteronyssinus 72%/78%, Alternaria 75%/81 %. Our results indicate that both in vitro tests are useful tools for the detection of specific IgE antibody.