THE RAPID 1-2-3® HEMA CASSETTE HEPATITIS C (HCV) TEST
The RAPID 1-2-3® HEMA CASSETTE HEPATITIS C (HCV) TEST is a rapid fourth generation two site sandwich immunoassay for the detection of total antibodies specific to Hepatitis C virus (HCV) in human whole blood, serum, or plasma. The test employs a genotype cross- reactive recombinant antigen derived from the core, NS3, NS4 and NS5 regions of multiple HCV genotypes. The double antigen sandwich system ensures detection of all anti-HCV antibody isotypes IgG, IgM, IgA etc to all major HCV-genotypes.
Hepatitis C virus (HCV) is a single stranded RNA virus containing a linear genome with a length of about 9,600 nucleotides with positive polarity. It is now recognized that HCV infection is the major etiological agent of post-transfusion hepatitis type non-A, non-B. HCV infection typically progresses to chronic liver disease. On the basis of polygenetic analysis, HCV has been grouped into six major genotypes, each containing one or more subtypes. The distribution of HCV genotype varies in different geographical areas.
The first generation HCV antibody became commercially available in the early 1990s and was widely used. As more reactive recombinant antigens were identified from conserved regions of the HCV genome, newer serological assays (second and third generation) were introduced.
Third generation assays were introduced in the late 1990s. In these assays, a recombinant NS5 antigen has been added to the antigens used in the second generation assays. These third generation assays have higher sensitivities and specificities than the second generation and are much less strongly influenced by the infecting genotype.
The first, second and third generation HCV antibody assays still lack sensitivity in seroconversion or show inexplicable discrepancies with confirmatory assays. This is primarily due to cross reactivity with the current HCV genotype 1 antigen-based assays. To solve this problem, fourth generation assays using antigens from multiple HCV genotypes, including genotypes 1, 2, 3, containing universally conserved epitopes, are being developed and evaluated.
PRINCIPLES OF THE TEST
The RAPID 1-2-3® HEMA CASSETTE HEPATITIS C (HCV) TEST is a fourth generation assay that uses a multi-epitope recombinant peptide antigen cocktail that is broadly cross-reactive to all major HCV genotypes. Moreover, RAPID 1-2-3â HEMA CASSETTE HEPATITIS-C (HCV) TEST detects total anti-HCV antibodies ensuring detection of all antibody isotypes viz., IgG, IgM, IgA, etc.
The RAPID 1-2-3® HEMA CASSETTE HEPATITIS C (HCV) TEST utilizes the principle of immunochromatography, a unique two site immunoassay on a nitrocellulose membrane. The conjugate pad contains two components – a multi-epitope HCV recombinant peptide antigen conjugated to colloidal gold and a rabbit IgG conjugated to colloidal gold. As the test specimen flows through the membrane test assembly the HCV recombinant peptide antigen-colloidal gold conjugate complexes with HCV antibodies in the specimen and travels on the membrane due to capillary action along with the rabitt IgG-colloidal gold conjugate. This complex moves further on the membrane to the test region ‘T’ where it is immobilized by another multi-epitope HCV recombinant peptide antigen coated on the membrane leading to formation of a colored band. The absence of this colored band in the test region indicates a negative test result.
The remaining conjugate and unbound complex, if any, along with rabbit IgG gold conjugate move further on the membrane and are subsequently immobilized by the goat anti-rabbit antibodies coated on the membrane at the control region (C), forming a pink-purple colored band. This control band acts as a procedural control and serves to validate the test results.