title: Diagnosis and incidence of delayed pressure urticaria in patients with chronic urticaria.
abstract: BACKGROUND
  The incidence of delayed pressure urticaria (DPU) may have been underestimated, particularly in patients with widespread wheals of concurrent idiopathic urticaria, because of difficulty in recognizing the association between pressure-related swellings and the preceding physical stimulus. Diagnostic tests for DPU have not been done routinely in studies of urticaria and have not been compared.
  
  
  OBJECTIVE
  Our purpose was to establish the incidence of DPU and other physical urticarias in patients with chronic urticaria and to compare two reproducible pressure challenge tests.
  
  
  METHODS
  One hundred thirty-five patients were tested for immediate dermographism, for DPU and, when indicated by the history, for cholinergic and/or cold urticaria. In patients with pressure-related symptoms, pressure challenge testing with a dermographometer (100 gm/mm2) was compared with a test that involves the application of 1.5 cm diameter weighted rods and more closely resembles a naturally occurring pressure stimulus.
  
  
  RESULTS
  Physical urticarias were present in 96 patients (71%). Thirty patients (22%) had immediate dermographism, 50 (37%) had DPU, 15 (11%) had cholinergic urticaria, and 3 (2%) had cold urticaria. A 70-second pressure challenge with the dermographometer gave results comparable to the use of the weighted rods.
  
  
  CONCLUSIONS
  DPU appears to be more common in chronic urticaria than previously reported and is present in some patients who do not report pressure-related wheals.
authors.affiliation: St. John's Institute of Dermatology, St. Thomas's Hospital, London, U.K.
authors.forename: R J
authors.initials: RJ
authors.lastname: Barlow
authors.forename: F
authors.initials: F
authors.lastname: Warburton
authors.forename: K
authors.initials: K
authors.lastname: Watson
authors.forename: A K
authors.initials: AK
authors.lastname: Black
authors.forename: M W
authors.initials: MW
authors.lastname: Greaves
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002908:Chronic Disease; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011312:Pressure; D012680:Sensitivity and Specificity; D013997:Time Factors; D014581:Urticaria / Q000175:diagnosis* / Q000453:epidemiology*