Comparison between specific IgE levels and skin prick test results of local and imported American cockroach, dog, cat, dust mites and mold allergen extracts

Background: Skin prick test (SPT) and specific IgE (sIgE) are approved for evaluation of allergen sensitization. Local allergen extracts are less expensive and more available but need to be standardized. Objective: To compare SPT results of local and imported allergen extracts and sIgE levels in response to the American cockroach, dog, cat, Dermatophagoides pteronyssinus (Dp), Dermatophagoides farinae (Df) and Cladosporium spp. allergens. Method: This prospective, randomized, double-blind, self-controlled study was performed in respiratory allergic volunteers. Each subject was pricked with local and imported allergen extracts and sIgE levels were measured. Results: The agreement between SPT results from each local and imported allergen extract was statistically significant, and the level of agreement for dog allergens was very good (kappa > 0.8). All patients with a positive SPT in response to imported Dp allergen extract had positive SPT in response to local Dp allergen extract. Mean wheal diameter of each allergen in both groups showed significant correlation with sIgE levels. The correlation coefficient (CC) for cat allergens showed a very good-to-excellent relationship (CC>0.75). When compared with sIgE levels, SPT results for imported and local allergen extracts showed comparable sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio (LR)+ and LR-. Conclusions: When the SPT results are compared between local and imported allergen extracts, all were found to have significant agreement, with very good agreement for cat allergens. When the SPT results are compared with specific IgE levels, both local and imported allergen extract provided comparable validity.