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Molecular assays such as the AMPLICOR and COBAS AMPLICOR HCV MONITOR® tests, as well as the recently introduced High Pure/COBAS TaqMan HCV Test, are used to determine baseline viral load and changes in viral load during treatment (eg week 12). A qualitative test should be utilised, such as the AMPLICOR or COBAS AMPLICOR HCV Tests, v2.0, to confirm infection and assess outcome of therapy.
The AMPLICOR HCV MONITOR® Test, v2.0 is the industry standard test used to quantify viral load and monitor patients’ response on therapy. However, the next generation COBAS TaqMan HCV Test provides up to a 7 log linear range for an accurate viral load determination throughout the clinically-relevant range of HCV infection. The outcome of therapy is related to the HCV RNA levels prior to treatment; high baseline viral loads resulting in lower rates of sustained viral response (Davis and Lau, 1997; Martinot-Peignoux et al, 2000). The qualitative AMPLICOR and COBAS AMPLICOR HCV tests, with a lower limit of detection of 50 IU/mL can be used to determine whether treatment has resulted in a sustained viral response.
The High Pure/COBAS TaqMan HCV Test, recently developed by Roche for the quantitative determination of HCV RNA levels, offers automated, closed-tube amplification and detection, minimising potential testing errors due to user intervention and contamination. It enables optimal monitoring of treatment success and early detection of treatment failure through enhanced sensitivity, specificity and broad linear range.
Liver biopsies are often used to support diagnosis, assess disease severity (necroinflammation and fibrosis) and assess therapeutic effectiveness (Perrillo, 1997; Brunt, 2000; Saadeh et al, 2001). Recent consensus treatment guidelines have moved away from recommending biopsy in all patients prior to initiating therapy (French Consensus Conference Statement: Treatment of Hepatitis C, 2002; National Institutes of Health Consensus Statement, 2002).
Prior to the introduction of HCV RNA tests, serum alanine aminotransferase (ALT) measurements were often used to assess responses to therapy. However, ALT is an unreliable marker of liver damage since the absolute measure of serum ALT does not correlate with the degree of severity of liver disease (Kaplan, 2002). Although very high ALT levels are generally associated with hepatocellular damage and can, in many instances, provide an indication of underlying disease, low levels of ALT are not always associated with mild liver disease and ALT levels tend to drop in advanced cirrhosis. As biochemical responses do not always correlate well with the virological response (Marcellin et al, 1999; 2001), viral RNA determination is now considered the ‘gold standard’ for monitoring on-treatment response to pegylated IFNα therapy.