title: Primary and Secondary Thrombotic Microangiopathy Referred to a Single Plasma Exchange Center for Suspected Thrombotic Thrombocytopenic Purpura: 2000-2011.
abstract: BACKGROUND
  Patients who present with unexplained thrombocytopenia, that is, hemolytic anemia with end-organ dysfunction with a normal coagulation profile are suspected to have thrombotic thrombocytopenic purpura (TTP) and are usually referred to a plasma exchange (PE) center for immediate treatment to prevent mortality. Here, we describe the distribution and outcomes of patients with suspected TTP referred to a single center for PE therapy.
  
  
  METHODS
  In this retrospective cohort study, we reviewed the data of all consecutive patients who were treated with PE for suspected TTP at our center between January 2000 and December 2011 (Canada). Patients were followed for a median of 73 months.
  
  
  RESULTS
  Of 137 patients, 70 (51%) were determined to have primary (idiopathic) TTP and 67 (49%) secondary TTP or hemolytic uremic syndrome (HUS). Patients with primary TTP were twice as likely to be refractory than those with secondary TTP or HUS: 27 vs. 12%; p = 0.03. Patients with primary TTP were more likely to experience remission (61/70 (87%) vs. 45/67 (67%); p = 0.01); however, the relapse rate was higher in patients with primary versus secondary TTP-HUS: 11 vs. 1.5%, respectively (p = 0.03). The overall mortality rate was 23% (13 vs. 33% in those with primary vs. secondary TTP-HUS; p = 0.007). After excluding deaths from scleroderma renal crisis (100% mortality), malignancy (75% mortality) and stem cell transplant (50% mortality), the survival rate for secondary TTP was 85%.
  
  
  CONCLUSIONS
  In contrast to patients with secondary TTP or HUS, those with primary TTP have a higher refractory and relapse rate, but are also more likely to achieve remission and survive.
authors.affiliation: Department of Medicine, Division of Nephrology, Western University and London Health Sciences Centre, London, Ont., Canada.
authors.forename: Randah
authors.initials: R
authors.lastname: Dahlan
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Sontrop
authors.forename: Lihua
authors.initials: L
authors.lastname: Li
authors.forename: Omar
authors.initials: O
authors.lastname: Ghadieh
authors.forename: William F
authors.initials: WF
authors.lastname: Clark
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000150:complications; D001424:Bacterial Infections / Q000150:complications; D003240:Connective Tissue Diseases / Q000150:complications; D005260:Female; D006463:Hemolytic-Uremic Syndrome / Q000175:diagnosis / Q000209:etiology* / Q000628:therapy*; D006801:Humans; D007155:Immunologic Factors / Q000627:therapeutic use; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D010314:Partial Thromboplastin Time; D010951:Plasma Exchange; D011697:Purpura, Thrombotic Thrombocytopenic / Q000175:diagnosis / Q000628:therapy*; D012008:Recurrence; D012017:Referral and Consultation; D012189:Retrospective Studies; D000069283:Rituximab / Q000627:therapeutic use; D015996:Survival Rate; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D007155:Immunologic Factors; D000069283:Rituximab