RESUMO
BACKGROUND: Many companies have developed different methods and products for allergen-specific immunoglobulin E (IgE) tests. Because there is no standardised reference method, external quality assessment (EQA) is important for allergen-specific IgE test to ensure the comparability and reliability of the results from different laboratories. We prepared specimens for EQA of allergen-specific IgE tests and evaluated their stability. METHODS: Four pooled sera with 24 selected allergen-specific IgE levels were prepared and stored at −80℃. The stability of allergen-specific IgE levels was assessed on days 1, 7, and 14 at −20℃, 2℃ to 8℃, and 20℃ to 25℃, and then after 3 months at −80℃. Mock proficiency tests were performed with the four sets of prepared external quality controls for six laboratories, using the commercial multiple allergen simultaneous test (MAST) methodology. RESULTS: About 150 specimens (650 µL each) for EQA were prepared; randomly selected specimens showed similar IgE levels for the 24 allergens (±1 class). The levels of allergen-specific IgE remained stable throughout the study period (P>0.05). Although mock survey results from six laboratories using four MAST assays revealed some variability with a difference (2–3 class), no consistent differences were observed through the allergens or MAST methods. Qualitative results from the mock survey showed 85.4% (cut-off of class 1) and 81.3% (cut-off of class 2) concordance with the results from ImmunoCAP (Phadia, Sweden). CONCLUSIONS: The pooled sera prepared for allergen-specific IgE tests might be adequate and useful for EQA.