Analysis of ImmunoCAP(R) ISAC Results of Chronic Spontaneous Urticaria Patients: Comparison with Skin Prick and the MAST-EIA Tests

Kim, Ji Hoon; Roh, Joo Young; Lee, Jong Rok

Abstract

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(R) 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.