Analysis of ImmunoCAP® ISAC results of chronic spontaneous urticaria patients: Comparison with skin prick and the MAST-EIA tests

Background: In vivo and/or in vitro diagnostic tests to identify possible allergens have been conducted for patients with chronic spontaneous urticaria (CSU) in order to identify any predisposing factors and avoid unnecessary restrictions. Objective: The purpose of this study was to evaluate the diagnostic effectiveness of ImmunoCAP® ISAC (ISAC) in CSU patients. Methods: A total of 31 patients with CSU were tested by ISAC and Multiple Allergen Simultaneous Test enzyme immunoassays (MAST-EIA). A skin prick test (SPT) was performed for 17 out of 31 patients. The results of ISAC and MAST-EIA were evaluated based on the SPT results. Results: For 17 patients, with SPT used as the reference standard, ISAC compared with MAST-EIA showed lower sensitivity (22.2% vs. 26.5%), higher specificity (100% vs. 95.7%), higher positive predictive value (100% vs. 52.9%), and lower negative predictive value (86.9% vs. 87.7%). The agreement rate was more favorable for ISAC than for MAST-EIA (87.3% vs. 85.1%; kappa=0.324 vs. 0.263). For 31 patients, the agreement rate between ISAC and MAST-EIA was 83.9% for both Dermatophagoides farinae and Dermatophagoides pteronyssinus. Correlation coefficients (Rho) between ISAC and MAST-EIA for each allergen were 0.690 and 0.675, respectively. Conclusion: For CSU patients, specificity, positive predictive value, and the agreement rate of ISAC were similar or superior to those of MAST-EIA. In addition, ISAC provides valuable information on the possible sensitization to different allergen sources by elucidating cross-reactive components. With careful clinical correlations in interpretation, ISAC can be a useful diagnostic tool to detect allergens in CSU patients.