The atopy patch test: is it time to redefine its significance?

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AbstractOBJECTIVE:

The atopy patch test (APT) was recently defined as an important tool in the diagnosis of atopic eczema/dermatitis syndrome (AEDS). Recent data showed that the APT may be positive also in patients with rhinitis or asthma. We examined the mechanisms that could underlie such findings.

DATA SOURCE:

To locate relevant articles pertaining to the use of APT, MEDLINE databases from 1989 (when the APT was first introduced) to the present were searched.

STUDY SELECTION:

Articles concerning the results of APT in patients with AEDS and with rhinitis or asthma attributable to sensitization to inhalant allergens were examined.

RESULTS:

Recent data show that APT to dust mites is frequently positive, and it may be the only positive test, not only in subjects with AEDS but also in subjects with only respiratory symptoms (rhinitis, asthma) and a history of AEDS. Instead, positive skin prick tests and in vitro immunoglobulin (Ig) E tests prevail in patients with a negative history for AEDS.

CONCLUSION:

Based on the pathophysiology of AEDS, in which the mechanisms of delayed hypersensitivity are predominant, the APT seems to have a greater significance than skin prick tests or in vitro IgE tests in patients with current or past history of AEDS. That different sensitization mechanisms underlie these different clinical expressions seems conceivable. In particular, if mite allergens enter the skin in the presence of a filaggrin-dependent skin barrier dysfunction, the sensitization mechanism seems to be ultimately revealed by a positive APT.

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