title: Risk of immune thrombocytopenic purpura and autoimmune hemolytic anemia among 120 908 US veterans with hepatitis C virus infection.
abstract: BACKGROUND
  There is emerging evidence that hepatitis C virus (HCV) infection play a role in the etiology of immune thrombocytopenia purpura (ITP) and autoimmune hemolytic anemia (AIHA), both of which are severe autoimmune cytopenias.
  
  
  METHODS
  To determine if HCV infection increases the risk for ITP and AIHA, we calculated the incidence rates of ITP and AIHA among 120 691 HCV-infected and 454 905 matched HCV-uninfected US veterans who received diagnoses during the period 1997 to 2004. After excluding individuals with a prior diagnosis of a lymphoproliferative disease, human immunodeficiency virus, or cirrhosis, we fitted Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) as measures of risks.
  
  
  RESULTS
  We found 296 ITP and 90 AIHA cases. Among HCV-infected vs HCV-uninfected persons, the overall incidence rates of ITP were 30.2 and 18.5 per 100 000 person-years, and for AIHA they were 11.4 and 5.0 per 100 000 person-years, respectively. Hepatitis C virus was associated with elevated risks for ITP (HR, 1.8; 95% CI, 1.4-2.3) and AIHA (HR, 2.8; 95% CI, 1.8-4.2). The ITP incidence was increased among both untreated and treated HCV-infected persons (HR, 1.7; 95%, CI, 1.3-2.2 and HR, 2.4; 95% CI, 1.5-3.7, respectively), whereas AIHA incidence was elevated only among treated HCV-infected persons (HR, 11.6; 95% CI, 7.0-19.3).
  
  
  CONCLUSIONS
  Individuals infected with HCV are at an increased risk for ITP, whereas the development of AIHA seems to be associated with HCV treatment. It may be beneficial to test individuals newly diagnosed as having ITP for HCV infection.
authors.affiliation: Department of Medicine, Baylor College of Medicine, 2002 Holcombe Road, Houston, TX 77030, USA. echiao@bcm.edu
authors.forename: Elizabeth Y
authors.initials: EY
authors.lastname: Chiao
authors.forename: Eric A
authors.initials: EA
authors.lastname: Engels
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Kramer
authors.forename: Kenneth
authors.initials: K
authors.lastname: Pietz
authors.forename: Louise
authors.initials: L
authors.lastname: Henderson
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Giordano
authors.forename: Ola
authors.initials: O
authors.lastname: Landgren
mesh_terms: D000328:Adult; D000368:Aged; D000744:Anemia, Hemolytic, Autoimmune / Q000453:epidemiology* / Q000821:virology*; D016001:Confidence Intervals; D005500:Follow-Up Studies; D016174:Hepacivirus / Q000302:isolation & purification; D006526:Hepatitis C / Q000150:complications* / Q000188:drug therapy / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D016016:Proportional Hazards Models; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000453:epidemiology* / Q000821:virology*; D012367:RNA, Viral / Q000302:isolation & purification; D012107:Research Design; D014481:United States / Q000453:epidemiology; D014728:Veterans / Q000706:statistics & numerical data*
chemical_list: D012367:RNA, Viral