title: Detection limit of architect hepatitis C core antigen assay in correlation with HCV RNA, and renewed confirmation algorithm for reactive anti-HCV samples.
abstract: BACKGROUND
  hepatitis C infections are detected by anti-HCV screening tests. Reactive anti-HCV results give no information about the presence or absence of hepatitis C viruses, or of unspecific reactivity. To obtain information about the viral load, HCV RNA measurements, following a reactive anti-HCV result, are performed in well equipped and specialised laboratories. Anti-HCV immunoblots are the only means to exclude non specific reactivity. The measurement of HCV core antigen (HCV-Ag), as an alternative to HCV RNA, is discussed, as it can be analysed on the same instrument as anti-HCV.
  
  
  OBJECTIVE
  The detection limit of HCV-Ag is crucial to use it in lieu of HCV RNA, in regard of the different genotypes. A renewed algorithm is proposed to exclude unspecific reactivity of anti-HCV.
  
  
  METHODS
  Samples were tested on Architect i2000SR (Abbott) for anti-HCV and HCV-Ag. HCV RNA measurements were obtained by Cobas Ampliprep/Taqman (Roche) or m2000rt(®) (Abbott).
  
  
  CONCLUSIONS
  Comparison between HCV-Ag and HCV RNA from 126 samples of 101 patients with chronic hepatitis C gave linear regression R(2) 0.89, slope 0.885 and intercept -2.258, which were independent of the genotypes. The detection limit of HCV-Ag was between 2.4 and 4.5 Log(10)IU/mL. A renewed algorithm for confirmation of reactive anti-HCV results is proposed: active or resolved hepatitis C infections or false reactivity can be differentiated by sequenced reflex testing due to HCV-Ag, anti-HCV immunoblot and HCV RNA.
authors.affiliation: Cantonal Hospital of Aarau, Department of Laboratory Medicine, CH-5001 Aarau, Switzerland. Electronic address: cornelia.ottiger@ksa.ch.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Ottiger
authors.forename: Nicole
authors.initials: N
authors.lastname: Gygli
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Huber
mesh_terms: D000465:Algorithms; D000956:Antigens, Viral / Q000097:blood*; D016174:Hepacivirus / Q000302:isolation & purification*; D018937:Hepatitis C Antibodies / Q000097:blood*; D019698:Hepatitis C, Chronic / Q000175:diagnosis* / Q000821:virology*; D006801:Humans; D057230:Limit of Detection; D012367:RNA, Viral / Q000097:blood*; D019562:Viral Load / Q000379:methods*
chemical_list: D000956:Antigens, Viral; D018937:Hepatitis C Antibodies; D012367:RNA, Viral
keywords: Architect; CV%; EDTA; Ethylene diaminetetraacetic acid; HCV Ag; HCV PCR; HCV RNA; HCV core antigen; HCV genotype; HCV viral load; Hepatitis C; anti-HCV; coefficient of variation; hepatitis C virus core antigen; hepatitis C virus ribonucleic acid