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Increased sensitivity of the Roche COBAS AMPLICOR HCV test, version 2.0, using modified extraction techniques
Michael Stuart Forman1, Alexandra Valsamakis
1Division of Microbiology, The Johns Hopkins Medical Institutions, Meyer B1-193, 600 North Wolfe Street, Baltimore, MD 21287-7093, USA.
The Journal of Molecular Diagnostics : JMD
|July 23, 2004
Summary
Two new methods, ultraspin and ultracolumn, significantly enhance the sensitivity of the COBAS AMPLICOR HCV assay for detecting hepatitis C virus (HCV) RNA. These processing modifications improve detection limits across multiple HCV genotypes.
Area of Science:
- Virology
- Molecular Diagnostics
- Biochemistry
Background:
- The COBAS AMPLICOR HCV version 2.0 assay is a widely used method for detecting hepatitis C virus (HCV) RNA.
- Enhancing the sensitivity of existing diagnostic assays is crucial for early detection and effective management of viral infections.
- Current processing methods may have limitations in detecting low levels of viral RNA.
Purpose of the Study:
- To evaluate the impact of two novel specimen concentration techniques, ultraspin (centrifugation) and ultracolumn (cationic detergent plus silica membrane), on the sensitivity of the COBAS AMPLICOR HCV assay.
- To compare the performance of these modified processing methods against the standard assay method.
- To assess the specificity and potential for increased detection of HCV RNA in clinical specimens using the enhanced methods.
Main Methods:
- Modified the COBAS AMPLICOR HCV version 2.0 assay by incorporating ultraspin and ultracolumn specimen concentration steps.
- Tested the modified assays using commercial hepatitis C virus (HCV) preparations across various genotypes (1a, 1b, 2b, 3a, 4, 5a, 6a).
- Determined the limit of detection (LOD) for each genotype using standard, ultraspin, and ultracolumn methods.
- Re-tested clinical specimens negative by the standard assay using the modified methods to evaluate clinical sensitivity.
Main Results:
- The ultraspin method demonstrated improved LODs for all tested HCV genotypes compared to the standard method, ranging from 4 to 12 IU/ml.
- The ultracolumn method showed a significant increase in sensitivity, with LODs as low as 1.5 to 3 IU/ml for several genotypes.
- No false positives were observed with the ultraspin method.
- Re-testing of clinical specimens revealed that ultraspin detected HCV RNA in 3 out of 152 previously negative samples, and ultracolumn in 2 out of 109.
Conclusions:
- Both ultraspin and ultracolumn processing modifications substantially enhance the sensitivity of the COBAS AMPLICOR HCV assay.
- The ultracolumn method offers the greatest improvement in detecting low levels of HCV RNA.
- These modified methods hold promise for increasing the detection rate of HCV RNA in clinical specimens, potentially improving patient diagnosis.