| 1. Acute generalized exanthematous pustulosis (AGEP):
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| - Patch testing shall be performed for diagnostic purposes.
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| - The reliability and safety of intradermal tests are unclear, while delayed-reading skin prick or intradermal tests can be helpful [116].
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| - In a French study, 58% of 45 patients tested positive in patch testing following AGEP, but not only in relation to BLA [149], as well as seven of 14 patients in another study [150].
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| 2. Drug rash with eosinophilia and systemic symptoms (DRESS):
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| - Patch testing should be performed for diagnostic purposes.
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| - In an evaluation of 14 patients with a history of DRESS and positive patch testing to BLA, and 3 patients with a positive delayed reading after intradermal testing for BLA, none of the patients experienced symptom recurrence [149].
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| - Diagnostic testing revealed more than one allergen relevant to the previous DRESS in some of the patients (18% in [149]).
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| - The value of skin prick testing, as well as delayed-reading intradermal tests, remains unclear. Since recurrence has been described, these test methods should only be used in the case of an urgent/vital indication [116].
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| - T-cell in vitro diagnostics can be an instrument to identify the triggering agent in severe drug reactions such as bullous reactions and DRESS/DIHS.
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| 3. Fixed drug exanthema (FDE):
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| - Patch testing shall be performed for diagnostic purposes (in loco) [116].
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| 4. Symmetrical drug-related intertriginous and flexural exanthema (SDRIFE)
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| - Patch testing shall be performed for diagnostic purposes [116].
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| 5. Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN):
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| - Patch testing can be considered for diagnostic purposes.
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| - However, only scant positive results have been described for patch testing in SJS/TEN [78, 116].
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| - A literature search has not found any evidence as yet that skin testing can cause a renewed flare-up of TEN [112, 149].
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| - T-cell diagnostics can be considered in individual cases of SJS/TEN.
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| 6. Maculopapular exanthema:
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| - Patch testing shall be performed for diagnostic purposes. Delayed-reading intradermal testing is recommended if the preparation is available in parenteral form. Before IDT a skin prick test with an immediate-reading should be performed, a delayed reading can be considered.
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| 7. Anaphylaxis and drug-induced urticaria:
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| - Skin prick testing shall be performed for diagnostic purposes. The IDT test shall be performed for diagnostic purposes if available.
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| - Specific IgE determination shall be performed for diagnostic purposes if available.
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| - The basophil activation test can be helpful in some cases. |
