title: Establishing a sample-to cut-off ratio for lab-diagnosis of hepatitis C virus in Indian context.
abstract: BACKGROUND
  Lab-diagnosis of hepatitis C virus (HCV) is based on detecting specific antibodies by enzyme immuno-assay (EIA) or chemiluminescence immuno-assay (CIA). Center for Disease Control reported that signal-to-cut-off (s/co) ratios in anti-HCV antibody tests like EIA/CIA can be used to predict the probable result of supplemental test; above a certain s/co value it is most likely to be true-HCV positive result and below that certain s/co it is most likely to be false-positive result. A prospective study was undertaken in patients in tertiary care setting for establishing this "certain" s/co value.
  
  
  METHODS
  The study was carried out in consecutive patients requiring HCV testing for screening/diagnosis and medical management. These samples were tested for anti-HCV on CIA (VITROS(®) Anti-HCV assay, Ortho-Clinical Diagnostics, New Jersey) for calculating s/co value. The supplemental nucleic acid test used was polymerase chain reaction (PCR) (Abbott). PCR test results were used to define true negatives, false negatives, true positives, and false positives. Performance of different putative s/co ratios versus PCR was measured using sensitivity, specificity, positive predictive value and negative predictive value and most appropriate s/co was considered on basis of highest specificity at sensitivity of at least 95%.
  
  
  RESULTS
  An s/co ratio of ≥6 worked out to be over 95% sensitive and almost 92% specific in 438 consecutive patient samples tested.
  
  
  CONCLUSIONS
  The s/co ratio of six can be used for lab-diagnosis of HCV infection; those with s/co higher than six can be diagnosed to have HCV infection without any need for supplemental assays.
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Aseem K
authors.initials: AK
authors.lastname: Tiwari
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Pandey
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Avinash
authors.initials: A
authors.lastname: Negi
authors.affiliation: Department of Microbiology, Fortis Memorial Research Institute, Gurgaon, Haryana, India.
authors.forename: Ruchika
authors.initials: R
authors.lastname: Bagga
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Ajay
authors.initials: A
authors.lastname: Shanker
authors.affiliation: Department of Microbiology, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Usha
authors.initials: U
authors.lastname: Baveja
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Raina
authors.initials: R
authors.lastname: Vimarsh
authors.affiliation: Department of Gastroenterology, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Richa
authors.initials: R
authors.lastname: Bhargava
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Ravi C
authors.initials: RC
authors.lastname: Dara
authors.affiliation: Department of Transfusion Medicine, Medanta-The Medicity, Gurgaon, Haryana, India.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Rawat
keywords: Anti-hepatitis C virus tests; Center for Disease Control; chemiluminescence immuno-assay; polymerase chain reaction; testing algorithm