Investigation of the diagnostic performance of prick test with two environmental allergens in dogs with atopic dermatitis: A study using intradermal test as the gold standard

Abstract

Background There are no studies investigating the correlation between prick test (PT) and intradermal test (IDT) with environmental allergens in dogs with atopic dermatitis (AD). Objectives To investigate the correlation between PT and IDT for two environmental allergens, and to calculate the sensitivity, specificity and Youden index of PT, using IDT as the gold standard. Materials and methods Twenty‐two dogs with AD were selected. PT was performed with glycerinated allergen extracts, along with negative and positive controls, using the Greer Prick System. Reactions were interpreted (positive/negative) subjectively and by using seven objective criteria, by an examiner blinded to the IDT results. IDT reactions to the same allergens were interpreted, subjectively and objectively, by another masked investigator. The agreement between PT and IDT, the sensitivity, specificity and Youden index of PT, using IDT as gold standard, were calculated. Results On subjective evaluation, the correlation between PT and IDT was poor and sensitivity of PT was 0%. Of the seven criteria for the objective evaluation of PT, the best diagnostic performance was attained when allergen‐induced wheals were considered positive if their longest diameter was ≥8.5 mm. However, even then, the correlation with IDT was moderate, and the sensitivity of PT, albeit based on few positive IDT reactions, was low. Conclusion and Clinical Relevance At least as performed herein, PT has a poor‐to‐moderate correlation with IDT, mainly as a consequence of the lack of positive PT reactions. Further studies are needed to improve PT technique, yet, meanwhile, it cannot be recommended as a substitute for IDT.

Pilot study to determine the concordance between skin prick and intradermal test (IDT) reactivity to environmental allergens in atopic dogs using IDT as the gold standard

“…However, we have documented an overall marginal (47%) sensitivity for SPT (graded subjectively). A recently reported study showed even lower sensitivity (0%) when SPT and IDT reactions to two environmental allergens ( D. farinae and Lolium perenne ) were compared 11 . Although SPT fared better in our study, with sensitivities ranging from a high of 63% for dust mite mix and grass pollen mix to a low of 8% for mould mix no.…”

“…A recently reported study also documented very good specificity for SPT (>94%). 11 On balance, it is the poor sensitivity of SPT documented by these two studies that will require further investigation if veterinary allergists continue to be interested in utilising SPT in dogs.…”

“…Additionally, it is possible that the wheal reactions were not observed at an optimal timepoint. However, this seems unlikely considering the results of previous studies 6–9,11 . Most clinicians consider clinically relevant skin testing reactions to be those that are mediated via Type I (immediate) hypersensitivity.…”

“…Several new threshold criteria for positive reactions using objective parameters were investigated in a recent study. 11 All save for one resulted in poor correlation with subjective scoring. The one criterion noted to have moderate correlation with subjective grading was setting the threshold for a positive result as a wheal diameter >8.5 mm.…”

“…10 The more recent study, published in 2022, found that prick testing was 0% sensitive as compared to intradermal testing for two environmental allergens. 11 The primary objective of the study reported here was to determine the concordance between SPT and IDT for atopic dogs with representative allergen mixes (pollens, dust mites, moulds) using the GREER Pick system (Stallergenes Greer), including sensitivity, specificity, and positive and negative predictive values. Intradermal reactivity rates of the mixes also were compared to their individual allergen components.…”