title: Risk factors associated with chronic hepatitis C virus infection: limited frequency of an unidentified source of transmission.
abstract: OBJECTIVE
  Risk factors have been studied in patients with acute non-A, non-B hepatitis, and approximately 40-50% have no known risk factor for viral acquisition. A significant undefined source of viral transmission has been suggested. We sought to clearly delineate the risk factors in a population of patients with documented chronic hepatitis C virus (HCV) infection to assess the magnitude of HCV transmission without known risk factors.
  
  
  METHODS
  Risk factor profiles were carefully assessed in 301 consecutive patients with chronic HCV infection. Patients were classified by gender and age. Overall risk factor distributions were calculated and comparisons were made between groups to detect differences in mode of HCV acquisition.
  
  
  RESULTS
  One hundred ninety-six men and 105 women were studied; 223 were age < or = 45 yr and 78 were > 45 yr. Overall, 25% of patients had a history of transfusion and 49% had a history of intravenous drug use (i.v.DU). Only 12% had no history of risk factor exposure. Men were more likely to have a history of i.v.DU and less likely to have a history of blood transfusion or sexual exposure/household contact. Younger patients were more likely to have a history of i.v.DU and older patients were more likely to have a history of blood transfusion and to deny all risk factor exposure.
  
  
  CONCLUSIONS
  A careful history delineated a potential risk factor for HCV acquisition in 88% of patients with chronic HCV infection. Men and younger patients had different risk factor profiles than women and older patients, respectively. It is likely that an important unknown mode of HCV transmission occurs in a significant minority of patients.
authors.affiliation: Department of Medicine, Northwestern Memorial Hospital, Northwestern University Medical School, Chicago, Illinois 60611, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Flamm
authors.forename: R A
authors.initials: RA
authors.lastname: Parker
authors.forename: S
authors.initials: S
authors.lastname: Chopra
mesh_terms: D000328:Adult; D000367:Age Factors; D001803:Blood Transfusion; D003075:Coitus; D005260:Female; D019698:Hepatitis C, Chronic; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D015819:Substance Abuse, Intravenous