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Î After a thorough history and physical examination, no further
diagnostic testing might be appropriate for patients with CU.
• However, limited routine laboratory testing can be performed to exclude
underlying causes. Targeted laboratory testing based on clinical suspicion is
appropriate.
• Extensive routine testing for exogenous and rare causes of CU or immediate
hypersensitivity skin testing for inhalants or foods is NOT warranted. Routine
laboratory testing in patients with CU whose history and physical examination
lack atypical features rarely yields clinically significant findings. (C)
Î Screening for thyroid disease is of low yield in patients without
specific thyroid-related symptoms or history of thyroid disease.
Increased levels of anti-thyroglobulin or anti-thyroid antibodies
in euthyroid (ie, normal TSH) subjects are commonly detected,
although the clinical implications of this finding are unclear. (C)
Î Although commercial assays are now available, the utility of
testing for autoantibodies to the high-affinity IgE receptor or
autoantibodies to IgE has not been established. (C)
Î Patients with recurrent angioedema in the absence of coexisting
urticaria should be evaluated for hereditary angioedema, acquired
C1-inhibitor deficiency, or ACE inhibitor–associated angioedema
before a diagnosis of idiopathic angioedema is made. (C)
Î Skin biopsy can be performed when vasculitis is suspected, such
as in patients with refractory CU, or when other nonurticarial
immunologic skin diseases are a consideration. Routine skin
biopsy specimens are not required in most cases of CU. (D)
Î Immediate hypersensitivity skin or serologic testing for food
or other allergens is rarely useful and NOT recommended on a
routine basis. (D)
