Diagnosis of flea allergy dermatitis: comparison of intradermal testing with flea allergens and a FcepsilonRI alpha-based IgE assay in response to flea control.

The objective of this study was to evaluate the accuracy of in vivo and in vitro tests in the diagnosis of flea allergy dermatitis in comparison with history, clinical signs and response to flea control. Intradermal testing using four different sources of flea allergens and FcepsilonRIalpha-based immunoglobulin (Ig)E assays were performed in 15 flea-allergic dogs, 15 atopic dogs and 15 dogs infested with fleas but showing no clinical signs of skin disease. Sensitivity, specificity, negative predictive value, positive predictive value and accuracy were calculated for all five tests and results varied greatly. Sensitivity, specificity and overall accuracy were 27, 83 and 64%, respectively, for one extract (Isotec), 67, 90 and 82% for another extract (Greer), 93, 90 and 91% for flea saliva, 40, 90 and 73% for the recombinant Cte f 1 both produced by Heska Corp. and 87, 53 and 64% for a FcepsilonRIalpha-based IgE assay. These results indicate that intradermal testing with flea extracts is more accurate in the diagnosis of flea allergy dermatitis than in vitro tests. Moreover, pure flea saliva used as a reagent for intradermal testing provided the best results in terms of sensitivity, specificity and overall accuracy although the Greer extract, a whole body flea extract, also allowed a good correlation between intradermal testing results and clinical approach to flea allergy dermatitis diagnosis.