title: Simultaneous detection of hepatitis C virus antigen and antibodies in dried blood spots.
abstract: BACKGROUND
  Enzyme immunoassays (EIA) designed to detect hepatitis C virus (HCV) core antigen and anti-HCV antibodies (HCV AgAb) simultaneously can improve the early detection of HCV infection when molecular diagnostic methods are not widely available.
  
  
  OBJECTIVE
  To evaluate the suitability of dried blood spot (DBS) samples for detecting HCV AgAb using commercial EIAs.
  
  
  METHODS
  Paired serum and DBS samples were assayed using two commercial EIAs for HCV AgAb (Monolisa™ HCV AgAb ULTRA and Murex HCV AgAb). Manufacturer's recommendations were followed for sera while sample volume, incubation time and cut-off (CO) determination were evaluated for the DBS samples. The values of sensitivity, specificity, inter-rater agreement, detection limit, assay precision and stability of DBS samples at different conditions (22-26°C, 2-8°C and -20°C) were determined.
  
  
  RESULTS
  It was necessary to increase the DBS sample volume fourfold compared to the sera samples to approximate the DBS Optical Density (OD) values to the sera OD values. Using ROC curve to recalculate CO values for the DBS samples, sensitivity was 97.5% for both EIAs, while the specificity was 99.71% for Monolisa™ HCV AgAb ULTRA and 95.95% for Murex HCV AgAb. Accurate testing results were obtained with DBS samples for 60 days at all conditions evaluated; storage at -20°C resulted in low OD variation. Both EIAs demonstrated the same limit of detection among DBS samples [estimated viral load of 3.1 International Units per millilitre (IU/mL)] and low OD value variability in repetitivity and reproducibility studies.
  
  
  CONCLUSIONS
  DBS samples can be used for the detection of HCV AgAb by EIA as they present comparable performance characteristics and excellent stability among various storage conditions.
authors.affiliation: Federal Hospital from the Servers of the State of Rio de Janeiro, RJ, Brazil.
authors.forename: C P U
authors.initials: CP
authors.lastname: Brandão
authors.forename: B L C
authors.initials: BL
authors.lastname: Marques
authors.forename: V A
authors.initials: VA
authors.lastname: Marques
authors.forename: C A
authors.initials: CA
authors.lastname: Villela-Nogueira
authors.forename: K M R
authors.initials: KM
authors.lastname: Do Ó
authors.forename: M T
authors.initials: MT
authors.lastname: de Paula
authors.forename: L L
authors.initials: LL
authors.lastname: Lewis-Ximenez
authors.forename: E
authors.initials: E
authors.lastname: Lampe
authors.forename: J A
authors.initials: JA
authors.lastname: Sá Ferreira
authors.forename: L M
authors.initials: LM
authors.lastname: Villar
mesh_terms: D000328:Adult; D059788:Dried Blood Spot Testing / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D016174:Hepacivirus / Q000276:immunology*; D006526:Hepatitis C / Q000097:blood / Q000175:diagnosis* / Q000276:immunology / Q000821:virology; D018937:Hepatitis C Antibodies / Q000097:blood* / Q000276:immunology; D018936:Hepatitis C Antigens / Q000097:blood* / Q000276:immunology; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D018937:Hepatitis C Antibodies; D018936:Hepatitis C Antigens