What is the role of lab testing in the diagnosis of erythema annulare centrifugum (EAC)?

Updated: Mar 06, 2020
  • Author: Dirk M Elston, MD; Chief Editor: William D James, MD  more...
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Skin scrapings from lesional sites of erythema annulare centrifugum (EAC) should be analyzed after preparation in potassium hydroxide (KOH) to ascertain the presence or the absence of hyphae suggestive of tinea or candidiasis.

Lyme antibody titer helps exclude erythema migrans, and serological studies can exclude syphilis. [39]

An antinuclear antibody test should be performed in the appropriate clinical setting. Systemic lupus erythematosus is in the differential diagnosis of EAC, and Sjögren syndrome has been reported in association with EAC.

A purified protein derivative (PPD) test and an anergy panel can be used to help determine if an underlying M tuberculosis infection is present.

A complete blood count with differential can be used to evaluate a suspected underlying infection (neutrophilia with bacterial infection; eosinophilia with parasitic infection or hypereosinophilic syndrome).

If compatible with the clinical presentation of erythema annulare centrifugum, liver function studies may be useful because hyperbilirubinemia secondary to cholestasis and elevated transaminase levels secondary to hepatitis have been reported with EAC.

With an appropriate history of gastrointestinal complaints, a stool examination may be useful to search for ova and parasites (ascariasis has been reported with EAC).

For females, serum or urine beta-human chorionic gonadotropin testing may be indicated.

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