Diagnosis
- Diagnosis is based on patient’s history & physical exam
Classification
- Urticaria is classified as acute or chronic
- 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 wk in duration & usually w/o angioedema
- More common in children & young adults & tends to have a triggering event
Chronic Urticaria
- More common in adults (3rd & 4th decades of life), symptoms last >6 wk
Chronic Spontaneous Urticaria
- Urticaria that has spontaneously recurred at least 2x/wk for >6 wk w/ unknown causes
Inducible Urticaria
- Cold contact
- Delayed pressure
- Heat contact
- Symptomatic dermographism
- Daily lesions & 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 w/in 1-24 hr, have a central swelling of variable size surrounded by erythema & associated w/ itching, sometimes burning sensation
- Angioedema characterized by a sudden evident swelling of the lower dermis & subcutis which may last up to 72 hr
- 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 wk
RECOMMENDED DIAGNOSTIC TESTS FOR URTICARIA SUBTYPES | ||
Subtype | Test | Extended Diagnostic Tests |
Acute spontaneous | Presence of wheals/pruritus | None |
Chronic idiopathic spontaneous | Differential blood count & ESR or C-reactive protein (CRP), omission of suspected drugs (NSAIDs, ACE inhibitors, antibiotics) | Test for: Infectious diseases, type 1 allergy, autoantibodies, thyroid hormones, skin test, pseudoallergen-free diet for 3 wk, lesional skin biopsy*, autologous serum skin test |
Autoimmune chronic spontaneous | Autoreactivity, functional bioassay & immunoassay | Differential blood count, ESR/CRP cryoproteins |
Cold contact | Cold provocation & threshold test (eg ice cubes, cold water) | Differential blood count, ESR/CRP cryoproteins, rule out other diseases/infections |
Delayed pressure | Pressure test (0.2-1.5 kg/cm2 for 10 & 20 min) & threshold test | None |
Heat contact | Heat provocation & threshold test (eg warm water) | None |
Solar | UV & visible light of different wavelengths | Rule out other light-induced dermatoses |
Demographic | Test by stroking the arm | Differential blood count, ESR/CRP cryoproteins |
Aquagenic | Apply wet cloths set at body temperature for 20 min | None |
Cholinergic | Exercise & hot bath provocation | None |
Contact | Cutaneous provocation test, prick/patch test (see results after 20 min) | None |
Exercise-induced | History of urticaria after exercise, appearing w/ or w/o food intake but not after a hot bath | None |
Modified from: EAACI/GA2LEN/EDF/WAO guidelines: management of urticaria, 2013. *Lesional skin biopsy indicated for lesions lasting for >36 hr |
Assess disease activity of chronic spontaneous urticaria
- Several guidelines recommend using the Urticaria Activity Score (UAS7) system in assessing disease severity
- Summation of scores of symptoms during a 7-day period
- 1 = mild wheals (<20 wheals w/in 24 hr) + mild (nontroublesome) pruritus
- 2 = moderate wheals (20-50 wheals w/in 24 hr) + moderate (troublesome but does not interfere w/ daily activities or sleep) pruritus
- 3 = intense wheals (>50 wheals w/in 24 hr or large confluent wheals) + intense (severely troublesome, interferes w/ daily activities & sleep) pruritus