title: High antibody level: an accurate serologic marker of viremia in asymptomatic people with hepatitis C infection.
abstract: BACKGROUND
  The screening and diagnosis of hepatitis C virus (HCV) infection is initiated by testing for antibody to HCV (anti-HCV). A positive anti-HCV test in blood donors represents ongoing infection in only a variable proportion of individuals. Because a high anti-HCV level has been associated with viremia, a study was conducted to determine whether a high antibody level is an accurate serologic marker for viremia in asymptomatic anti-HCV-positive persons.
  
  
  METHODS
  In a diagnostic test study, we included 856 anti-HCV-positive blood donors in a blood bank at Guadalajara, Jalisco, Mexico, between 2002 and 2007. A third-generation amplified chemiluminescence assay (ChLIA HCV) was used to detect anti-HCV. A positive result of the qualitative nucleic acid test (HCV RNA) was considered the gold standard for viremia.
  
  
  RESULTS
  By receiver operating characteristic analysis, the signal-to-cutoff (S/CO) ratio of 20 or more was chosen as optimal to identify viremia and so was defined as high anti-HCV level. There was a significant difference in the proportion of viremia between subjects with high antibody level and those with lower levels (93.7% vs. 1.8%, respectively; p < 0.001). A high antibody level showed a sensitivity for viremia of 96.6% (95% confidence interval [CI], 93.8%-98.1%), a specificity of 96.6% (95% CI, 94.8%-97.8%), and a likelihood ratio of 28.6 (95% CI, 18.4%-44.6%).
  
  
  CONCLUSIONS
  A high antibody level (S/CO ratio >/=20 by ChLIA HCV) clearly divides the viremic from the nonviremic blood donors and functions as an accurate serologic marker to guide the use of routine HCV RNA testing to confirm hepatitis C infection.
authors.affiliation: Health Research Council in Jalisco State, Mexican Institute of Social Security, Jardines Vallarta, Zip Code 45120, Zapopan, Jalisco, México. acontreras53@hotmail.com
authors.forename: Ana M
authors.initials: AM
authors.lastname: Contreras
authors.forename: Rodolfo J
authors.initials: RJ
authors.lastname: Ochoa-Jiménez
authors.forename: Alfredo
authors.initials: A
authors.lastname: Celis
authors.forename: Claudia
authors.initials: C
authors.lastname: Méndez
authors.forename: Laura
authors.initials: L
authors.lastname: Olivares
authors.forename: Claudia E
authors.initials: CE
authors.lastname: Rebolledo
authors.forename: Isabel
authors.initials: I
authors.lastname: Hernandez-Lugo
authors.forename: Ana I
authors.initials: AI
authors.lastname: Aguirre-Zavala
authors.forename: Ricardo
authors.initials: R
authors.lastname: Jiménez-Méndez
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Chung
mesh_terms: D015415:Biomarkers / Q000097:blood; D001771:Blood Banks; D005260:Female; D006526:Hepatitis C / Q000097:blood*; D018937:Hepatitis C Antibodies / Q000097:blood*; D006801:Humans; D008163:Luminescent Measurements / Q000379:methods*; D008297:Male; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014766:Viremia / Q000097:blood*
chemical_list: D015415:Biomarkers; D018937:Hepatitis C Antibodies