Prospective analysis of epicutaneous testing for inhalant allergy: comparison of arm and back subsites with mRAST.

Objectives: 1) To compare epicutaneous testing (ET) from four skin subsites (forearm, upper arm, upper back, lower back) and 2) to compare ET to modified RAST (mRAST) for inhalant allergens.

Study Design: Prospective clinical trial.

Subjects And Methods: Fifty one patients underwent ET at four skin subsites and mRAST to six antigens and positive and negative controls.

Results: The forearm and upper back showed best sensitivity to positive controls and all subsites demonstrated similar specificity to negative controls. The forearm and upper back demonstrated best sensitivity and specificity for most antigens. No statistically significant differences were noted for antigen sensitivity and specificity for the four subsites. ET and mRAST agreed best on D. farinae and timothy grass and least on short ragweed and dog epithelium.

Conclusion: This study confirms that forearm and upper back demonstrate very good sensitivity and specificity for positive and negative controls and most tested antigens. This has important diagnostic implications for clinical practice of inhalant allergy.