Inter-laboratory comparison of semiquantitative allergen-specific Immunoglobulin E test: 7 years of experience in Korea

Introduction Multiple allergen simultaneous test (MAST) is widely used as a screening tool for allergic diseases and has the advantage of providing specific IgE (sIgE) results for various allergens in semiquantitative class. We have continuously conducted external quality assessment (EQA) since 2012 for clinical laboratories performing MAST using AdvanSure allergy screen test (LG CHEM, Korea). This study provides an account of the EQA experience. Methods Samples were prepared using pooled sera collected from patients with suspected allergic disease and sent to each laboratory twice a year. Each round included 4-6 serum samples with sIgE for 10-20 inhaled or food allergens. The acceptable class value was the most frequently reported MAST class +/- 1 titer that exceeded 80% of the total laboratory results. Results The average number of participating laboratories was 76 (49-90) and the average response rate was 97.3% during the entire survey period. The acceptable rates were consistently high at 97.7% +/- 3.7%. Of the total 537 trials, 18 trials (3.4%) were regarded as nonconsensus results, in which acceptable answers did not exceed 80%. For unacceptable results, the false-negative rate (1.5% +/- 2.8%) was higher than the false-positive rate (0.8% +/- 2.7%) (p < 0.001). MAST class results were correlated with quantitative IgE results by ImmunoCAP (Spearman's correlation coefficient of 0.682 (p < 0.001) and gamma index of 0.777 (p < 0.001). Conclusion Although EQA for MAST showed a high level of acceptable answer, some allergen assays require harmonization. Continuous performance of systematic EQA is needed to improve the accuracy of sIgE assays and quality control in clinical laboratories.