urticaria
URTICARIA
Urticaria is characterized by sudden appearance of wheals and/or angioedema.
The intensity of the pruritus varies but may be severe enough to disrupt sleep, work or school.
It is classified acute if the urticaria has been present for <6 weeks and chronic if >6 weeks. A specific cause is more likely to be identified in acute cases.
It can be triggered by immunological or nonimmunological mechanism.

Urticaria Diagnosis

Diagnosis

  • Diagnosis is based on patient’s history and physical examination

Classification

  • Urticaria is classified as acute or chronic, and as spontaneous (no triggering factor) or inducible (a particular triggering factor is identified)
    • A specific cause is more likely to be identified in acute cases
  •  Can be triggered by immunological or non-immunological mechanism

Acute Urticaria

  • Lesions occurring ≤6 weeks in duration and usually without angioedema
  • More common in children and young adults and tends to have a triggering event
  • Routine laboratory work-ups are not required, except when the cause of the urticaria points to a type I food hypersensitivity or other triggering factors like medications [eg non-steroidal anti-inflammatory drugs (NSAIDs)]

Chronic Urticaria

  • More common in adults (3rd and 4th decades of life), symptoms last >6 weeks

Chronic Spontaneous Urticaria

  • Presence of wheals, angioedema or both for >6 weeks due to factors that are identifiable or idiopathic

Inducible Urticaria

  • Cold urticaria
  • Delayed pressure urticaria
  • Heat urticaria
  • Symptomatic dermographism
    • Daily lesions and recurrent episodic lesions are not differentiated
  • Solar urticaria
  • Vibratory angioedema
  • Aquagenic urticaria
  • Cholinergic urticaria
  • Contact urticaria

Autoimmune Chronic Spontaneous Urticaria (ACU)

  • Proposed gold standard for diagnosis of ACU (combination of all 3 parameters):
    • Positive bioassay [eg basophil histamine release assay (BHRA), basophil activation marker expression] AND
    • Positive autoreactivity [eg positive autologous serum skin test (ASST)] AND
    • Positive immunoassay for specific IgG autoantibodies against FcεRIα and/or anti-IgE

Physical Examination

Look for typical lesions of urticaria

  • Wheals which typically are fleeting, lasting within 30 minutes-24 hours, have a central swelling of variable size surrounded by erythema and associated with itching, sometimes burning sensation
  • Angioedema characterized by a sudden evident swelling of the lower dermis and subcutis or mucous membranes, that is sometimes painful which may last up to 72 hours
  • Lesions may appear on any part of the body

Stroke the arm to test for dermographism/dermatographism

  • Discontinue antihistamine therapy for at least 2-3 days, immunosuppressive therapy for at least a week

Chronic Urticaria

  • Diagnostic examinations are based on the patient’s history and physical examination

Chronic Spontaneous Urticaria

  • Consider other possible diagnoses in patients with presentations indicative of chronic urticaria
  • Further tests are requested if indicated by the patient’s history and physical examination, most notably in patients with chronic and/or on-and-off disease presentation
  • Assess disease activity of chronic spontaneous urticaria
    • Several guidelines recommend using the Urticaria Activity Score (UAS7) system in assessing disease severity and treatment effectivity
    • Summation of scores of symptoms during a 7-day period
      • 0 = no wheals, no pruritus
      • 1 = mild wheals (<20 wheals within 24 hours) + mild (nontroublesome) pruritus 
      • 2 = moderate wheals (20-50 wheals within 24 hours) + moderate (troublesome but does not interfere with daily activities or sleep) pruritus 
      • 3 = intense wheals (>50 wheals within 24 hours or large confluent wheals) + intense (severely troublesome, interferes with daily activities and sleep) pruritus

Chronic Inducible Urticaria

  • Provocation threshold measurements are used to assess disease activity, while the urticaria control test (UCT) is used to determine how well the disease is prevented from recurring
RECOMMENDED DIAGNOSTIC TESTS FOR URTICARIA SUBTYPES
Subtype Test Extended Diagnostic Tests1
(Based on the patient's history)
Spontaneous Urticaria
Acute spontaneous urticaria None None2
Chronic spontaneous urticaria Differential blood count, erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) Perform tests for: Infectious illnesses, functional autoantibodies [eg autologous serum skin test (ASST)], allergy, thyroid abnormalities, presence of chronic inducible urticaria, severe systemic illnesses, others (skin biopsy)
Inducible Urticaria
Cold urticaria Cold provocation and threshold test (eg ice cubes, cold water) Differential blood count and ESR or CRP, rule out other diseases/infections
Delayed pressure Pressure test (0.2-1.5 kg/cm2 for 10 and 20 minutes) and threshold test None
Heat urticaria Heat provocation and threshold test (eg warm water) None
Solar Ultraviolet (UV) and visible light of different wavelengths and threshold test Rule out other light-induced dermatoses
Symptomatic dermographism Test by stroking the arm and threshold test Differential blood count, ESR or CRP 
Vibratory angioedema Test using vibration (eg mixer, Vortex) None
Aquagenic Provocation test/apply wet cloths set at body temperature for 20 minutes None
Cholinergic Exercise and hot bath provocation, threshold test None
Contact Cutaneous provocation test, prick/patch test (see results after 20 minutes) None
Exercise-induced History of urticaria after exercise, appearing with or without food intake but not after a hot bath None
Modified from: The European Academy of Allergology and Clinical Immunology (EAACI)/Global Asthma and Allergy European Network (GA2LEN)/European Dermatology Forum (EDF)/World Allergy Organization (WAO) guideline for the definition, classification, diagnosis and management of urticaria. Allergy. 2018; EAACI/GA2LEN/EDF guideline: definition, classification and diagnosis of urticaria. Allergy. 2006.
1Depends on the cause being considered
2Except when the patient’s history indicates the need for testing
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