Clinical Relevance of Patch Test Reactions

Abstract

Reading patch test results cannot be limited to scoring as positive or negative. Scoring in itself has no meaning if it is not linked in some way with the medical history of the patient. In other words, a positive patch test (and to some extent a negative patch test) has no interest if it is not labeled as relevant or nonrelevant. Incidentally, this concept is valid also for all laboratory investigations. To diagnose allergic contact dermatitis, two significant steps should be considered:1. Demonstrating the existence of contact allergy to one or several allergens ~2. Demonstrating their clinical relevance ~ The first step is fulfilled when a positive patch test reaction deemed to reveal the presence of a genuine contact hypersensitivity is obtained. This involves assessing the morphology of the reaction and deciding whether it represents a true-positive allergic reaction as opposed to a false-positive one.