title: Incidence of thrombotic thrombocytopenic purpura/hemolytic uremic syndrome.
abstract: BACKGROUND
  Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome are rare disorders characterized by platelet aggregation, microthrombi, and resulting tissue damage. We studied the incidence and possible risk factors for these diseases in 3 large populations in the United States, United Kingdom, and Canada.
  
  
  METHODS
  Data were derived from a large health insurer in the United States, general practices in the United Kingdom, and the Province of Saskatchewan. We identified potential cases of thrombotic thrombocytopenia purpura and hemolytic uremic syndrome in computerized data and verified them by medical record review. We estimated incidence rates for thrombotic thrombocytopenia purpura and hemolytic uremic syndrome together and separately, and we conducted a case-control study to evaluate potential risk factors.
  
  
  RESULTS
  The age-sex standardized incidence of thrombotic thrombocytopenia purpura and hemolytic uremic syndrome was higher than previously reported (6.5, 2.2, and 3.2 per million per year in the United States, United Kingdom, and Saskatchewan, respectively), but there was no secular trend. The incidence of thrombotic thrombocytopenia purpura and hemolytic uremic syndrome was higher in women than men. Most cases of hemolytic uremic syndrome occurred before 20 years of age. We confirmed several known risk factors for thrombotic thrombocytopenia purpura and hemolytic uremic syndrome (cancer, bone marrow transplantation, pregnancy).
  
  
  CONCLUSIONS
  The incidence of thrombotic thrombocytopenia purpura and hemolytic uremic syndrome is higher than previously reported but does not appear to be rising. Apparent international differences in incidence could be the result of imprecision in identifying thrombotic thrombocytopenia purpura and hemolytic uremic syndrome in large research databases.
authors.affiliation: Ingenix, Newton, Massachusetts 02466, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Miller
authors.forename: James A
authors.initials: JA
authors.lastname: Kaye
authors.forename: Kathleen
authors.initials: K
authors.lastname: Shea
authors.forename: Najat
authors.initials: N
authors.lastname: Ziyadeh
authors.forename: Clorinda
authors.initials: C
authors.lastname: Cali
authors.forename: Corri
authors.initials: C
authors.lastname: Black
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Walker
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006463:Hemolytic-Uremic Syndrome / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D016347:Medical Records Systems, Computerized; D008875:Middle Aged; D011237:Predictive Value of Tests; D011697:Purpura, Thrombotic Thrombocytopenic / Q000453:epidemiology* / Q000209:etiology / Q000401:mortality; D012307:Risk Factors; D012525:Saskatchewan / Q000453:epidemiology; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology