Validation of a New ImmunoCAP TM Test for Detecting Allergen-Specific IgE to Two Spotted Spider Mite

Abstract

RATIONALE: Two spotted spider mite (TSM) is one of the most prevalent allergens in South Europe and Far East Asian countries, however, there has been no commercial kit available for detecting IgE antibodies to TSM. The aim of this study was to validate a new ImmunoCAPTM test for detecting allergen-specific IgE to TSM in serum. METHODS: 131 subjects with allergic rhinitis and/or asthma sensitized to TSM, and 60 non-atopic healthy controls were enrolled. Skin prick test was performed with home made TSM extract and skin reactivity was presented as allergen to histamine (A/H) ratio. ELISA coated with homemade TSM extract, and ImmunoCAPTM (Pharmacia Diagnostics AB, Sweden) were applied to measure allergen-specific IgE antibodies in serum. For confirming binding specificity, ELISA and ImmunoCAP inhibition tests were done with additions of TSM and D. pteronyssinus allergens. RESULTS: The percentage of patients with allergen-specific IgE by ELISA and ImmunoCAP were 28% vs. 50% among ≥2+ A/H responders and 50% vs. 62% among ≥3+ A/H responders, i.e. the higher skin reactivity the better correlation. Positive correlation was found between ImmunoCAP and ELISA (r=0.61, p<0.05). ImmunoCAP inhibition tests showed significant dose dependent inhibitions with addition of TSM, while minimal inhibitions with D. pteronyssinus. CONCLUSIONS: A new ImmunoCAP test for detecting allergen-specific IgE antibodies to TSM in serum was superior to ELISA system, and can be used for screening TSM sensitive patients in clinical practice.