Evaluation of the use of a combined HCV antigen/antibody assay in routine laboratory practice.
BACKGROUND
Combined hepatitis C virus (HCV) antigen/antibody (Ag/Ab) assays offer the advantage of a shorter window phase compared to traditional anti-HCV antibody assays. These assays have been extensively evaluated for the screening of healthy blood donors, but not in routine laboratory practice.


METHODS
We evaluated the performance of the combined HCV Ag/Ab assay Monolisa Ultra and compared it to Monolisa anti-HCV Plus (which only detects anti-HCV antibodies) in 61 HCV RNA-positive patients (genotypes 1 to 5) and in 276 consecutive AxSYM HCV-reactive patients. Discordant sera were tested with immunoblot and PCR.


RESULTS
All 61 PCR-positive sera were positive with AxSYM, Monolisa Ultra, and Monolisa Plus. Of the 276 consecutive AxSYM-reactive patients, 177 were confirmed as HCV-positive, 78 were HCV-negative and 21 were HCV-indeterminate. There were 4 false-positive results with Monolisa Ultra compared to 1 false-positive result with Monolisa PLus. The signal/cut-off ratio in immunoblot-negative sera was significantly higher with HCV Ultra compared to HCV Plus (p < 0.01). Sensitivity and specificity in AxSYM-reactive sera were 99.4% and 94.9% for Monolisa Ultra and 99.4% and 98.7% for Monolisa Plus.


CONCLUSIONS
When used as a secondary test, the sensitivity of the combined HCV Ag/Ab assay Monolisa Ultra was excellent, but specificity was reduced in AxSYM-reactive sera compared to Monolisa Plus.
Vermeersch
P
P
Laboratoriumgeneeskunde, Universitaire Ziekenhuizen Leuven, Leuven, België.
Van Ranst
M
M
Lagrou
K
K
D019411:Clinical Laboratory Techniques / Q000379:methods*; D003955:Diagnostic Tests, Routine; D005838:Genotype; D016174:Hepacivirus / Q000276:immunology; D006526:Hepatitis C / Q000175:diagnosis* / Q000276:immunology; D018937:Hepatitis C Antibodies / Q000097:blood*; D018936:Hepatitis C Antigens / Q000097:blood*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D015151:Immunoblotting / Q000379:methods; D016133:Polymerase Chain Reaction; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
D018937:Hepatitis C Antibodies; D018936:Hepatitis C Antigens; D011933:Reagent Kits, Diagnostic