investigations
Last reviewed 01/2018
Investigations:
- diagnosis is mainly clinical
- a careful history and examination will be sufficient to make the diagnosis
in most of the patients
- 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
- a careful history and examination will be sufficient to make the diagnosis
in most of the patients
- 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
- the duration of weal's can be used to differentiate the clinical patterns
of urticaria:
- ordinary urticaria - weals usually lasts from 2 to 24 hours
- contact urticaria - upto 2 hours
- physical urticaria - disappear within an hour, in delayed pressure urticaria takes upto 2-6 hours to develop and upto 48 hours to fade
- urticarial vasculitis - persist for days
- angioedema - can last upto 3 days without treatment (2)
Reference:
- 1. Clinical Knowledge Summaries 2007. Urticaria
- 2. British Association of Dermatologists 2007. Guidelines for evaluation and management of urticaria in adults and children