Which lab studies are used in the workup of chronic urticaria?

Updated: Jul 31, 2018
  • Author: Marla N Diakow, MD; Chief Editor: William D James, MD  more...
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Answer

The diagnosis of chronic urticaria is largely clinical and based on a thorough history and physical examination. A limited set of laboratory studies may be indicated for some patients in the diagnosis of chronic urticaria, and these include the following:

  • Complete blood cell (CBC) count with differential: The eosinophil count may be elevated in patients with parasitic infections, especially in developing countries, or in patients experiencing a drug reaction

  • Examination of the stool for ova and parasites: Should be considered in patients with gastrointestinal tract symptoms, an elevated eosinophil count, or a positive travel history

  • Erythrocyte sedimentation rate (ESR): May be elevated in persons with urticarial vasculitis

  • Antinuclear antibody (ANA) titers: Indicated when urticarial vasculitis is suspected

  • Hepatitis B and C titers: Hepatitis B and C may be associated with cryoglobulinemia, which is associated with some forms of cold-induced urticaria and urticarial vasculitis

  • Serum cryoglobulin and complement assays: Cryoglobulinemia is associated with some forms of cold-induced urticaria

  • Complement assays: C3 (associated with pulmonary involvement in a subset of patients with urticarial vasculitis), C4 (sometimes low in hereditary angioedema), and C1-esterase inhibitor (associated with hereditary angioedema) functional assays may be performed

  • Thyroid function testing and antithyroid microsomal and peroxidase antibody titers: Patients with urticaria unresponsive to antihistamines or steroids may have elevated titers [1] ; the plasma thyrotropin level (TSH) helps screen for thyroid dysfunction

  • Chronic Urticaria (CU) Index: A nonspecific measure of basophil histamine release, which, if positive, may indicate the presence of an autoantibody to the Fc receptor of immunoglobulin E (IgE)—that is, anti-FceR. These patients are likely to have an autoimmune basis for their disease

A skin biopsy is necessary in cases of suspected urticarial vasculitis or in cases of urticaria with atypical features on history and examination. It is also indicated for patients in whom individual urticarial lesions persist for more than 24 hours or are associated with petechiae or purpura, as well as for patients with systemic symptoms such as fever, arthralgia, or arthritis. A neutrophil-predominant pattern of urticaria on biopsy may represent a subtype that does not respond well to antihistamines.

See Workup for more detail.


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