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Investigations

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Investigations:

  • The diagnosis is mainly clinical
    • a careful history and examination will be sufficient to make the diagnosis in most of the patients. Laboratory tests are not indicated in cases of acute urticaria, unless there are findings on history and physical examination that would indicate the lesions were atypical (1)
      • detailed history - change in diet, medication; illness
      • examination - characteristic raised areas of the skin (weals) with redness in the surrounding area, blotchy areas can be seen when the weals fade before the surrounding area (1)
        • dermographism may be evident
  • the list of possible investigations is vast considering most cases are idiopathic
    • FBC - Hb, WBC, eosinophils, platelets
    • ESR
    • LFT's
    • Thyroid function test and thyroid autoantibodies
    • chest and sinus X-ray
    • urinalysis - bacteria
    • stool analysis - parasites
    • complement screen - including C1 esterase inhibitor
    • antinuclear antibody " skin biopsy - for urticarial vasculitis (2)
    • a good initial screening investigation is an ESR. (An elevated erythrocyte sedimentation rate or C-reactive protein may help distinguish urticarial vasculitis from urticaria. If there is high suspicion of urticarial vasculitis, a skin biopsy should be considered.)
  • the duration of weals can be used to differentiate the clinical patterns of urticaria:
    • ordinary urticaria - weals usually lasts from 2 to 24 hours
    • contact urticaria - up to 2 hours
    • physical urticaria - disappear within an hour, in delayed pressure urticaria takes up to 2-6 hours to develop and up to 48 hours to fade
    • urticarial vasculitis - persist for days
    • angioedema - can last up to 3 days without treatment (2)

Reference:

1. Zuberbier T, Abdul Latiff AH, Abuzakouk M, et al. The international EAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria. Allergy. 2022 Mar;77(3):734-66.

2. BSACI guideline for the management of chronic urticaria and angioedema. British Society for Allergy and Clinical Immunology (Feb 2015)

 


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