icon-folder.gif   Conference Reports for NATAP  
  NIH HCV Consensus Development Conference
June 10-12, 2002
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Diagnosing and Monitoring Tests in HCV For Patients: viral load, biopsy
Reported by Jules Levin
  Various tests are available for the diagnosis and monitoring of hepatitis C infection. Tests that detect antibody against the virus include the EIAs, which contain HCV antigens from the core and nonstructural genes, and the recombinant immunoblot assays (RIBAs). The same HCV antigens are used in both EIAs and the RIBAs. Targeted amplification techniques using either polymerase chain reaction (PCR) or transcription-mediated amplification (TMA) have been developed to detect HCV RNA. Liver biopsy can provide direct histologic assessment of liver injury due to HCV but cannot be used to diagnose HCV infection.
HCV Serologic Assays
EIA tests are reproducible, inexpensive, and FDA-approved for use in the diagnosis of HCV. They are suitable for screening at-risk populations and are recommended as the initial test for patients with clinical liver disease. The very high sensitivity and specificity of the third- generation EIAs (sensitivity greater than 99 percent, specificity 99 percent) obviate the need for a confirmatory RIBA in the diagnosis of individual patients, particularly those with risk factors for HCV. A negative EIA test is sufficient to exclude a diagnosis of chronic HCV infection in immune competent patients. Rarely, patients on hemodialysis and patients with immune deficiencies may have falsely negative EIAs. Conversely, falsely positive EIAs may occur in patients with autoimmune disorders. In these patients, assays for HCV RNA are necessary for diagnosis. RIBA remains a useful supplemental assay in the setting of large-scale HCV screening of blood products.
Qualitative HCV Assays
Persistent HCV infection in a patient with a positive EIA test should be confirmed by a qualitative HCV RNA assay. The automated, FDA-approved, qualitative HCV PCR assay has a lower limit of detection of 50 IU/mL. More recently, a transcription-mediated amplification assay has been developed with a lower limit of detection comparable to the qualitative PCR assay. This latter assay has yet to be approved for use by the FDA. The specificity of these assays exceeds 98 percent. A single positive qualitative assay for HCV RNA confirms active HCV replication, but a single negative assay does not prove that the patient is not viremic. A followup qualitative HCV RNA should be performed to confirm the absence of active HCV replication. Once HCV infection is confirmed, repeat testing for qualitative HCV RNA by qualitative PCR is not helpful in the management of untreated patients. Almost all patients remain viremic, and a negative result may merely reflect a transient decline in viral titer below the level of detection of the assay.
Quantitative HCV Assays
Testing for HCV RNA level (or viral load) by a quantitative assay, either quantitative PCR (qPCR) or branched DNA signal amplification assay (bDNA), can provide accurate information on HCV viral titer. An HCV RNA standard has been introduced to permit normalization of reported viral titers in international units (IU). The reported IU does not represent the actual number of viral particles in a preparation. Significant variability exists between available assays. The dynamic range of each assay needs to be observed, and appropriate dilutions of sample material should be performed to obtain accurate quantitative results. The clinical utility of serial HCV viral titers in a patient is predicated on continued use of the same specific quantitative assay used in the initial determination of the viral titer. While there is little correlation between disease severity or disease progression with the absolute titer of HCV RNA, quantitative determination of the HCV titer provides important information in assessing response to treatment.
Testing for serum ALT levels is the most inexpensive and noninvasive means of assessing disease activity. However, a single determination of ALT levels gives limited information about the severity of the underlying liver disease. In most studies, a weak association exists between the degree of ALT elevation and severity of the histopathological findings on liver biopsy. Serial determinations of ALT levels over time may provide a better means of assessing liver injury, but the accuracy of this approach has not been shown. Patients who initially have a normal ALT level should undergo serial measurements over several months to confirm the persistence of normal ALT levels. Although loss or reduction in HCV RNA is the primary indicator of response to antiviral therapy, the resolution of elevated ALT levels with antiviral therapy appears to be an important indicator of disease response. Serial determinations of ALT levels can be recommended as the general means of monitoring patients but is not adequate to assess progression to cirrhosis.
Various noninvasive tests have been examined for monitoring patients with chronic hepatitis C infection. These include routinely available laboratory tests, such as liver-associated chemistries, platelet count, and prothrombin time, as well as specific serum markers of fibrosis and inflammation that are not currently widely available or well validated. No single test or panel of serologic markers can provide an accurate assessment of intermediate stages of hepaticfibrosis. Similarly, quantitative tests of liver function and radiologic imaging of the liver are sensitive for diagnosing advanced cirrhosis but are not useful in assessing hepatic fibrosis and early cirrhosis.
Liver Biopsy
Liver biopsy yields information on fibrosis and histology assessment that is not obtainable by any other means. Various noninvasive methods based on biochemical or serologic tests have been evaluated in several studies. Liver enzymes have shown little value in predicting fibrosis. Extracellular matrix tests do predict severe stages of fibrosis but cannot consistently classify intermediate stages of fibrosis. Moreover, only liver biopsy provides information on possible contributions of iron, steatosis, and concurrent alcoholic liver disease to the progression of chronic hepatitis C toward cirrhosis. It is unusual for unexpected etiologies of liver disease to be discovered on liver biopsies from patients undergoing evaluation of chronic hepatitis C. The information obtained on liver biopsy does allow affected individuals to make more informed choices with regard to initiation or postponement of antiviral treatment. Adult or pediatric patients with persistently normal or slightly elevated ALT and minimal or no fibrosis on liver biopsy may be reassured of a favorable prognosis and decide to defer antiviral therapy. Since a favorable response to current antiviral therapy in patients infected with genotype 2 or 3 occurs in 80 percent, the necessity of routine pretreatment liver biopsy in these patients requires further study. Baseline assessment of liver histology offers the standard by which subsequent comparisons may be made. There is little information, however, on the appropriate interval for subsequent evaluations.
Hepatocellular Cancer Screening
HCC complicates cirrhosis secondary to HCV. It is estimated that HCC occurs after the development of cirrhosis at a rate varying from 0 to 3 percent per year. Few studies examine specific screening strategies for HCC in patients with advanced HCV. Alpha fetoprotein (AFP) and ultrasound every 6 months were used in a single study of patients with cirrhosis secondary to HCV. Identification of HCC was not significantly increased in the screened population.
Additional studies identifying new markers and testing specific screening protocols are warranted.