Pressure Urticaria Workup

Updated: Aug 08, 2016
  • Author: Sarah Beggs, MD; Chief Editor: Dirk M Elston, MD  more...
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Workup

Laboratory Studies

An elevated white blood cell (WBC) count or neutrophilia may be present. [23, 24] Complement levels are normal.

Some patients with delayed pressure urticaria (DPU) also have concomitant chronic idiopathic urticaria (CIU). The following ancillary testing can be helpful in patients with CIU [25, 26] :

  • The erythrocyte sedimentation rate (ESR), the C-reactive protein (CRP) level, or both may be elevated
  • Thyroid function tests and antibody testing for autoimmune thyroid disease may return positive results
  • Antibody testing for Helicobacter pylori can be performed; if results are positive, the infection should be treated
  • Testing for autoantibody to immunoglobulin E (IgE) can be performed
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Pressure Challenge Testing

Pressure challenge testing (with the dermographometer or the suspended-weight method) may be performed for delayed pressure urticaria (DPU). [27] Because therapy may influence test results, it is recommended that testing be performed at a time when therapy has been interrupted or stopped; however, some patients may have more severe disease that does not allow this. Repetitive testing can be used to assess response to therapy.

Multiple methods of applying measured amounts of pressure can be used to test for the development of DPU. A consensus conference review suggests using the following approaches [25] :

  • A shoulder strap 3 cm wide with a 7-kg weight for 15 minutes
  • A rod 1.5 cm in diameter with a 2.5-kg weight for 15 minutes
  • A rod 6.5 cm in diameter with a 5-kg weight for 15 minutes
  • A dermographometer to a pressure of 100 g/mm 2 for 70 seconds

The tests are most often applied to the shoulders, upper back, posterior thighs, or volar forearm. Pressure provocation tests should be read at 6 hours. Both the weight and the application time should be recorded. The duration of application is inversely related to the pressure applied; for example, wheals will take longer to develop with a lower pressure than with a higher pressure.

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Assessment of Urticaria Severity

Several scoring systems are used to measure the severity of chronic urticaria, both in research settings and in clinical practice. A useful assessment tool was suggested by a European panel (see the Table below). [26]

Table. Assessment Tool for Scoring Severity of Diseasea (Open Table in a new window)

Score Wheals Pruritus
0 None None
1 Mild (<20 wheals/24 h) Mild
2 Moderate (21-50 wheals/24 h) Moderate
3 Intense (>50 wheals/24 h) or large confluent areas Intense
aScore = wheal score (0-3) + pruritus score (0-3); thus, the overall score for severity ranges from 0 to 6.

The severity of delayed pressure urticaria (DPU) can vary throughout the day and from day to day. Overall disease activity is best assessed by having patients determine a severity score several times a day for several days before coming to their appointments.

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Histologic Findings

The histologic features of delayed pressure urticaria (DPU) lesions are variable, often depending on the age of the lesion. Biopsy within hours demonstrates moderate-to-heavy infiltration of eosinophils with neutrophils and lymphocytes in a perivascular and interstitial pattern in the dermis and subcutaneous fat. Degranulated mast cells may be noted. Biopsy of an older DPU lesion (>24 h) demonstrates eosinophils and lymphocytes.

No vessel-related changes (eg, leukocytoclasia or fibrinoid necrosis), such as those noted in urticarial vasculitis, are seen. Direct immunofluorescence test results are negative.

Several reports of bullous pressure urticaria have been reported, and histologic findings show spongiosis and intraepidermal bullae associated with an eosinophil-rich inflammatory infiltrate in the superficial and deep dermis. [9]

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