Drug allergy other diagnostic studies
(Redirected from Exanthematous pustulosis)
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Other Diagnostic Studies
- Skin testing- skin prick testing (SPT) pricks the skin with a tiny amount of the suspected allergen, and leads to the diagnosis of IgE mediated type I hypersensitivity reactions. These tests are standardized for penicillin, and are also useful for local anesthetics, muscle relaxants. These tests are also very sensitive for high-molecular-weight protein substances such as insulin and monoclonal antibodies. A negative test is useful for ruling out a penicillin allergy, however with other tests (except for with high-molecular-weight proteins), a negative test is not always useful for ruling out the presence of serum specific IgE. [1]
- Intradermal tests – these tests involve the injection of a small amount of allergen under the skin, into the dermis. Intradermal testing with delayed readout is more sensitive than a patch test, but carries a slightly higher risk of adverse allergic reactions when compared to skin testing. It tests for the same compounds as a skin prick test, and also leads to the diagnosis of IgE mediated hypersensitivity reactions. A prick test should be done beforehand, and the concentration used should be non-irritating.
- In-vitro tests for immediate drug reactions are available, but are largely considered investigational.
- Patch testing – this type of testing is useful for the diagnosis of various delayed type IV cutaneous reactions such as exanthemata, acute generalized exanthematous pustulosis, and flexular exanthema. It involves placing an aluminum disc containing allergens mixed with petrolatum on a patient’s back for 48 hours. The patient is then assessed for any reactions that may have occurred. This type of testing is not helpful to the diagnosis of Stevens-Johnson syndrome or toxic epidermal necrolysis and is contraindicated in anyone with a history of these conditions. [2]
- Skin biopsy may be useful to distinguish between Stevens-johnson syndrome and toxic epidermal necrolysis, and also to rule out other conditions on the differential diagnosis list.
- Histamine and tryptase levels- these test have shown to be useful in confirming the diagnosis of acute IgE mediated reactions, in particular anaphylaxis. Negative results do not rule out an anaphylactic reaction.
References
- ↑ Warrington R, Silviu-Dan F (2011). "Drug allergy". Allergy Asthma Clin Immunol. 7 Suppl 1: S10. doi:10.1186/1710-1492-7-S1-S10. PMC 3245433. PMID 22165859.
- ↑ Friedmann PS, Ardern-Jones M (2010). "Patch testing in drug allergy". Curr Opin Allergy Clin Immunol. 10 (4): 291–6. doi:10.1097/ACI.0b013e32833aa54d. PMID 20485160.