title: Twice-daily plasma exchange for patients with refractory thrombotic thrombocytopenic purpura: the experience of the Oklahoma Registry, 1989 through 2006.
abstract: BACKGROUND
  Twice-daily plasma exchange has been used for patients with thrombotic thrombocytopenic purpura (TTP) who are unresponsive to treatment with daily plasma exchange for many years but with no clear evidence of effectiveness.
  
  
  METHODS
  The 18 years' experience of The Oklahoma TTP-HUS (hemolytic-uremic syndrome) Registry, 1989 through 2006, with twice-daily plasma exchange for 31 episodes of TTP in 28 patients is reported. A definite response to twice-daily plasma exchange was defined a priori as a platelet (PLT) count increase after twice-daily plasma exchange on two separate occasions during the treatment of a single episode of TTP, with no change of other treatments. A possible response was defined as a PLT count increase after initiation of twice-daily plasma exchange only once with or without change of other treatments.
  
  
  RESULTS
  A definite response to twice-daily plasma exchange occurred in 3 episodes (three patients), 27 episodes had a possible response, and 1 episode had no response. The three patients with a definite response had ADAMTS13 activities of 5, 6, and 12 percent and all had an inhibitor; the patient with no response was subsequently determined to have Rocky Mountain spotted fever.
  
  
  CONCLUSIONS
  Twice-daily plasma exchange was typically considered in acutely ill patients who had initially responded but then severe thrombocytopenia recurred, often with new neurologic abnormalities, while continuing daily plasma exchange. In three patients, twice-daily plasma exchange appeared to be beneficial. In most patients, a benefit of twice-daily plasma exchange could not be clearly documented because other treatments were initiated or intensified.
authors.affiliation: Department of Biostatistics and Epidemiology, College of Public Health, The University of Oklahoma Health Science Center, Oklahoma City, OK 73190, USA.
authors.forename: Loan
authors.initials: L
authors.lastname: Nguyen
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Li
authors.forename: Deanna
authors.initials: D
authors.lastname: Duvall
authors.forename: Deirdra R
authors.initials: DR
authors.lastname: Terrell
authors.forename: Sara K
authors.initials: SK
authors.lastname: Vesely
authors.forename: James N
authors.initials: JN
authors.lastname: George
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010951:Plasma Exchange / Q000706:statistics & numerical data*; D011697:Purpura, Thrombotic Thrombocytopenic / Q000453:epidemiology*; D012042:Registries; D013997:Time Factors