Abstract
Background: Skin prick test (SPT) is the gold standard in the assessment of allergic sensitivities due to inhalants allergens. Serum specific IgE (SSIgE) measurement by ImmunoCAP is a complementary test with the antigen extracts derived from European antigens.Aim and Objective: The aim is to evaluate the correlation of SSIgE results with gold standard SPT against cockroach, housefly and mosquito, 3 aeroallergens which are frequently implicated in driving respiratory allergies in India.Methods: Fifty patients (15-50 yr, mean 28.5 yr) diagnosed with bronchial asthma and/or allergic rhinitis underwent SPT. SSIgE levels were obtained at the same visit. Sensitivity, specificity, positive and negative predictive values (PPV and NPV) of SSIgE testing were calculated using SPT as a gold standard. The correlation between SPT grading and SSIgE levels was also evaluated.Results: The study included 50 patients; 29 males and 21 females. Among the 3 aero-allergens, cockroach SSIgE had highest sensitivity (74.3%) and PPV (91.1%), however NPV (37.5%) and specificity (54.5%) being the lowest. On the contrary, housefly SSIgE had highest specificity (86.6%) and NPV (54.5%) but lowest sensitivity (68.7%) and PPV (78.5%). The two tests were in agreement (i.e., both positive or both negative) in 70% (cockroach), 78% (mosquito) and 62% (housefly). The study also observed a significant positive correlation between the grades of SPT reaction and SSIgE level for all the 3 aero-allergens.Conclusions: SSIgE using antigen extracts of cockroach and housefly from a different geographical region seem to give comparable results, and can thus be reliably used in evaluation of allergy.