title: Blood group O and black race are independent risk factors for thrombotic thrombocytopenic purpura associated with severe ADAMTS13 deficiency.
abstract: BACKGROUND
  It has been postulated that blood group O subjects may be partially protected against thrombotic thrombocytopenic purpura (TTP) because they have lower plasma levels of von Willebrand factor.
  
  
  METHODS
  The Oklahoma TTP Registry enrolled 301 consecutive patients from November 13, 1995 (when systematic ADAMTS13 measurements began), through 2009; 281 (93%) patients had ADAMTS13 measurements. Patients were designated as having severe ADAMTS13 deficiency when the activity measurement by either method was less than 10%. ABO blood group was determined in all 281 patients. The observed frequency of blood group O was compared to the expected frequency. The association between severe ADAMTS13 deficiency and blood group, race, sex, and age were analyzed by logistic regression.
  
  
  RESULTS
  The frequency of blood group O was unexpectedly and significantly greater than the race-ethnicity-adjusted expected frequency in 65 patients with severe ADAMTS13 deficiency (60.0% vs. 47.4%, p = 0.042) but not in 216 patients without severe ADAMTS13 deficiency (44.9% vs. 46.5%, p = 0.639). Blood group O and race-ethnicity were independently associated with severe ADAMTS13 deficiency among patients with TTP. The probability for severe ADAMTS13 deficiency was 45.8% with O and 32.1% with non-O blood groups for black patients and 24.1% with O and 15.1% with non-O blood groups for white patients.
  
  
  CONCLUSIONS
  Among patients with TTP and severe ADAMTS13 deficiency the relative frequency of patients with blood group O was greater than expected, suggesting that blood group O may be a risk factor for TTP associated with severe ADAMTS13 deficiency.
authors.affiliation: Department of Biostatistics and Epidemiology, College of Public Health, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73126-0901, USA.
authors.forename: Deirdra R
authors.initials: DR
authors.lastname: Terrell
authors.forename: David G
authors.initials: DG
authors.lastname: Motto
authors.forename: Johanna A
authors.initials: JA
authors.lastname: Kremer Hovinga
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lämmle
authors.forename: James N
authors.initials: JN
authors.lastname: George
authors.forename: Sara K
authors.initials: SK
authors.lastname: Vesely
mesh_terms: D000017:ABO Blood-Group System; D051722:ADAM Proteins / Q000172:deficiency*; D000071120:ADAMTS13 Protein; D000293:Adolescent; D000328:Adult; D001741:Black or African American; D000367:Age Factors; D000368:Aged; D001213:Asian; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D007198:Indians, North American; D008297:Male; D008875:Middle Aged; D009825:Oklahoma / Q000453:epidemiology; D011446:Prospective Studies; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood* / Q000208:ethnology*; D012307:Risk Factors; D012737:Sex Factors; D044465:White People; D055815:Young Adult
chemical_list: D000017:ABO Blood-Group System; D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human