Polymerase Chain Reaction (PCR) Assays for Hepatitis C Virus (Quantitative)
Hepatitis C Virus is considered to be the principle etiologic agent responsible for 90-95% of the cases of post-transfusion non-A and non-B hepatitis. The presence of anti-HCV antibodies in patients infected with HCV has led to the development of immunoserological assays that are specific for these antibodies. The presence of anti-HCV antibodies, however, is a measure of prior exposure to HCV infection, but cannot be considered as a marker for current infection. At the present time, an immunological assay for the direct detection of HCV antigen is unavailable. In addition, direct detection by viral culture methods is also not available. Therefore, there is no method currently available to provide a quantitative measure of HCV viremia.

Measurement of alanine aminotransferase levels (ALT) is considered to be a surrogate indicator of HCV infection, but is not a direct measure of viremia. The degree of ALT elevation cannot be directly correlated to the level of HCV infection. In fact, ALT can be elevated due to a number of causes of liver inflammation including, but not restricted to, viral hepatitis. In contrast, detection and quantification of HCV viremia by Polymerase Chain Reaction (PCR) nucleic acid amplification offers a measure of active viremia. (Kessier et al., 1996 and Reichard et al., 1993), Using PCR, it is possible to detect HCV viremia prior to immunological sero-conversion (Oritto et al., 1993 & Puoti et al., 1992) and to detect fluctuation of viremia in antibody-positive chronic HCV patients undergoing therapy with interferon (Young et al., 1993).

Principles of the Procedure
This test is based on five major processes: Specimen preparation, reverse transcription of target RNA to generate complementary DNA, PCR amplification of target cDNA using HCV specific complimentary primers, hybridization of amplified products to probes specific to the target, calorimetric detection and comparison of reading to a standard calibration curve drawn from PCR done on control samples with known viral loads.

COBAS AMPLICOR™ HCV MONITOR Test, v2.0

	Quantification of HCV over the range of 600-500,000 IU/mL
	Automated HCV quantification which may contribute to greater laboratory productivity
	Measurement of changes in serum or plasma HCV RNA levels
	Sensitivity, reliability and standardization in every test
	Accurate diagnosis of current infection and the ability to follow response to treatment
	Sensitive, reliable and rapid diagnosis and monitoring of viral infections in patients

	Kessier. H. H., Santner. B.I., Umalauft F. et al. 1996. Quantification and genotyping of Hepatitis C virus RNA in sera of hemo-dialysis and AIDS patients, Clinical Diagnostic Virology 5: 73-78.
	Oritto, E., Mizokami, M., Nakano, T., et al. 1993. Hepatitis C virus RNA level as a predictor of subsequent response to interferon-alpha therapy in Japanese patients with Chronic Hepatitis C. Journal of Medical Virology 44: 410-414.
	Puoti, M., Zonaro, A., Ravagil, A. et al. 1992. Hepatitis C virus RNA and antibody response in the clinical course of acute Hepatitis C virus infection. Hepatology 16: 877-881.
	Reichard, O., Yun, Z. B., Sinnerborg, A. et al. 1993. Hepatitis C viral titers in serum prior to during and after oral treatment with ribavirin for chronic Hepatitis C. Journal of Medical Virology 41: 99-102.
	Young, K., Ravafil, A. et al. 1993. Detection of Hepatitis C virus RNA by a combined reverse transcriptase-polymerase chain reaction assay. Journal of Clinical Microbiology 31: 882-886.