Intradermal tests in dermatology-II: Tests for noninfectious diseases

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INTRODUCTION Although the tests could be done at any site, the proximal part of the flexor aspect of the forearm is Intradermal tests are widely used to support the conventionally used. This site can be conveniently diagnosis of dermatological and nondermatological exposed and the skin of the proximal area is more diseases. They are mainly indicated for the detection sensitive than the distal. of immediate (Type I hypersensitivity) and delayed type hypersensitivity (DTH, Type IV hypersensitivity) INTERPRETATION OF INTRADERMAL TESTS towards exogenous or endogenous antigens. Intradermal tests for the diagnosis of infectious The optimal time for reading the reaction depends diseases in relevance to dermatovenereology are upon the pharmacological agent used for the test discussed in this section. and the type of immunological reaction to be observed. Intradermal tests for the detection of DTH Intradermal tests for the diagnosis of infectious are read at 48h, although they can be read as early diseases are listed in Table 1. They are indicated to as 12h and as late as four days. (The lepromin test detect DTH to organisms or their antigens. is read at four weeks and depends on the formation of a granuloma, which is a measure of cell-mediated Before undertaking intradermal test, it is advisable to immunity.) The size of the induration is more stop or avoid systemic steroids or immunosuppressive important than erythema while interpreting Type agents at least three days before the procedure as IV hypersensitivity. moderate to large doses of corticosteroids may inhibit a DTH reaction.