title: Signal to cut-off (S/CO) ratio and detection of HCV genotype 1 by real-time PCR one-step method: is there any direct relationship?
abstract: BACKGROUND
  Polymerase chain reaction (PCR) methods play an essential role in providing data related to diagnosis, monitoring and treatment of hepatitis C virus (HCV) infection. EIA results are reported as ''reactive'' or ''non reactive'' and EIA S/CO ratio may also be reported as ''high'' or ''low.'' This study aimed to evaluate the performance of a real-time RT-PCR and assess whether there is relationship between S/CO and PCR results.
  
  
  METHODS
  Sera from blood donors were analyzed by Enzyme-Linked Immunosorbent Assay (ELISA) and RT-PCR assay to detect HCV infection.
  
  
  RESULTS
  The RT-PCR assay to genotypes 1a/b showed an acceptable linear response in serial dilutions. The samples were divided into two groups based on their serological results: group A--S/CO ratio < 3 (60 samples) and group B--S/CO ratio > 3 (41 samples). Viral loads were confirmed positive in group B samples in 90%, and in group A samples were confirmed positive in only 13% by RT-PCR.
  
  
  CONCLUSIONS
  The methodology used was able to detect the presence of RNA-HCV genotype I in 90% of the samples serologically positive in group B. All negative samples were sent to search for other genotypes of HCV (genotypes 2-6) and were confirmed as negative. These data suggests that these negative samples may have HCV RNA viral load below the detection limit of our test (310 IU/ mL), or a false positive result in serological test, or spontaneous viral clearance occurred.
authors.affiliation: Associação Beneficente de Coleta de Sangue, Av. Jandira 1260, São Paulo, SP, Brazil. albertonig@nefro.epm.br
authors.forename: Guilherme
authors.initials: G
authors.lastname: Albertoni
authors.forename: C P
authors.initials: CP
authors.lastname: Arnoni
authors.forename: P R B
authors.initials: PR
authors.lastname: Araújo
authors.forename: F O
authors.initials: FO
authors.lastname: Carvalho
authors.forename: J A
authors.initials: JA
authors.lastname: Barreto
mesh_terms: D001782:Blood Donors; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005838:Genotype; D016174:Hepacivirus / Q000235:genetics* / Q000276:immunology; D006526:Hepatitis C / Q000175:diagnosis*; D018937:Hepatitis C Antibodies / Q000097:blood; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods; D012367:RNA, Viral / Q000032:analysis*; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D019562:Viral Load
chemical_list: D018937:Hepatitis C Antibodies; D012367:RNA, Viral