3RD-GENERATION RECOMBINANT IMMUNOBLOT ASSAY - COMPARISON OF REACTIVITIES ACCORDING TO HEPATITIS-C VIRUS GENOTYPE

Background: Recombinant immunoblot assay (RIBA) is widely used as a su pplemental test in hepatitis C virus (HCV) confirmatory algorithms. As this assay is based on HCV type 1, its performance was examined with the common European HCV genotypes (1, 2, and 3). Study Design and Meth ods: A study was performed to retest in third-generation RIBA (RIBA-3) all 146 second-generation RIBA (RIBA-2)-positive polymerase chain rea ction-positive samples detected by second-generation enzyme-linked imm unosorbent assays and having known HCV genotypes (74 HCV type 1, 21 ty pe 2, 51 type 3). RIBA band intensities were examined according to HCV genotype. An additional 90 RIBA-3-confirmed PCR-positive samples (47 HCV type 1, 5 type 2, 38 type 3) detected by third-generation enzyme-l inked immunosorbent assays were also examined. Results: In the first g roup of 146 samples, the RIBA-3 NS4 (c100p) band showed a marked impro vement in sensitivity for the detection of HCV types 2 and 3 over that of the c100 antigen of RIBA-2, but the mean band intensities of HCV t ypes 2 and 3 remained significantly lower than those of type 1, Improv ed sensitivity of the NS3 band of RIBA-3 to HCV type 3 was also appare nt, but, again, the mean band intensity measured was lower for type 3 than for either type 1 or type 2. The c22 band of RIBA-2 and RIBA-3 ex hibited equal sensitivity for all HCV genotypes. These differences wer e also apparent when RIBA-3 was used in conjunction with third-generat ion enzyme-linked immunosorbent assays. Conclusion: The current RIBA-3 lacks sensitivity to the NS4 antibody for HCV types 2 and 3. The inco rporation of type-specific components to other genotypes for NS4 (and NS3) antigens should be considered by the manufacturers.