Assessment of HBV and HCV Disease

Virological assessment of HBV infection

Dr Angelos Hatzakis, from the Athens University (Greece), reviewed the virological assessment of HBV infection. He mentioned that among serological markers, which define the infection status of an HBV-infected patient, HBsAg immunoassays have improved, having now a sensitivity of 89.3%-99.8%, and a specificity of 97.6%-100%. However, the emergence of surface mutants provides a continuous challenge to design more effective immunoassays. He also pointed out that in HIV/HBV-coinfected patients abnormal immunological profiles are more common (e.g., HBsAg+/anti-HBs+ and occult HBV).

 HBV DNA quantification has also evolved, and there are now commercially available assays with increased sensitivity that give a more accurate estimate, decisively helping in treatment initiation and monitoring of response to HBV therapy.

Thus, the Cobas Taqman 48 HBV^® (Roche Molecular Systems) detects HBV DNA within a range between < 10² to 10⁸ IU/mL [8]. However, during the discussion it was highlighted that these assays are not uniformly used and there is a need for standardization. On the other hand, IU/mL are now used while we still continue following guidelines that have made the recommendations based on copies/mL.

There is no agreement on the threshold indicating significant liver disease, and as Dr. Pawlotsky stated, ‘we only know that lower is better than higher. There is no agreement either on the definition of response to therapy (HBV DNA ¯ ³ 1log₁₀).

Of importance are also the genotypic drug resistance assays. Dr Hatzakis underlined that in HIV/HBV-coinfected subjects, the development of lamivudine (3TC) resistance mutations not only is more frequent, but also more complex patterns of mutations have been reported, and some mutants show in vitro characteristics of ‘vaccine escape’ mutants.

Current efforts are now focused on the standardization of drug resistance assays, on the assessment of kinetics of hepatic cccDNA, (a novel HBV marker that shows promise in monitoring response to therapy), and on research of novel resistance mutations and patterns.

Virological assessment of HCV infection

Dr. Xavier Forns, from the Hospital Clinic, Barcelona, addressed the virological assessment of HCV infection. The first tool is the detection of anti-HCV antibodies. Third generation ELISA assays (core, NS3, NS4, NS5) have sensitivity and specificity above 99% in immunocompetent patients with active replication. The estimated ‘window’ period of HCV antibody detection after acute infection is estimated in 3-8 weeks, but may be wider in HIV/HCV-coinfected patients. In addition, severely immunosuppressed individuals may lose the anti-HCV antibody.

Plasma HCV RNA quantification is important, not only at baseline to predict response to therapy, but also for monitoring. Due to the higher HCV RNA levels in HIV/HCV-coinfected compared to HCV-monoinfected patients, assays with a broad dynamic range seem more appropriate. ASR Cobas TaqMan 48 (Roche Molecular Systems), with a range from <10² to >10⁸, will probably be the standard of care, according to Dr. Forns.

HCV genotyping is important due to the implications in response to therapy. Methods relying on sequence analysis are more appropriate since serotyping assays have shown a lower sensitivity in HIV/HCV-coinfected subjects. Higher incidence of mixed HCV genotypes infections also have been reported in coinfected cohorts.

It is possible that successive infections with different genotypes [intravenous drug users (IDU), hemophiliacs] might have occurred, but the phenomenon might also be due to false reactivity. Higher sensitivity for mixed infections has been shown by Sequence analysis NS5b (Truegene^®, Bayer).

In Dr. Forns’ point of view, future research needs in the field include application of very sensitive methods to identify individuals with high probability of recurrence after antiviral therapy, and to refine HCV kinetics during antiviral therapy to individualize treatment.

Assessment of liver damage (Dr. Nezam Afdhal, Beth Israel Deaconess Medical Center, Boston).

Liver biopsy remains the ‘gold standard’ for the grading of inflammation and staging of liver disease. However, liver biopsies have ‘cons’, including the invasive character of the procedure (table 1). Therefore, non-invasive tools are emerging to assess liver fibrosis.

Table 1.  Pitfalls of liver biopsy and of serum markers of fibrosis.

There are currently 6 available serological tests, with FibroTest being the most validated. Their specificity ranges from 41% to 91% and their sensitivity from 41% to 90%. The problem in HIV infection is that there are several markers that may be dependent on HIV-related factors: transaminase elevation may reflect drug hepatotoxicity, total bilirubin may be elevated by certain antiretrovirals (indinavir and ATV), thrombocytopenia may be caused by the HIV infection, and the MELD score system for transplant candidates is not validated for HIV-infected patients.

Two studies have assessed serum markers of fibrosis in HIV/HCV-coinfected subjects: SHASTA index (hialuronic acid, AST and albumin) and the FIB-4 (age, platelets, AST, ALT). Limitations of serum tests are summarized in table 1.

Hepatic elastography (FibroScan®), a technique developed to measure liver elasticity has recently been validated alone and in combination with serum markers for HCV-monoinfection, and it is currently being studied in HIV-infected cohorts. It is easy to perform, but it better discriminates advanced stages of fibrosis [9]. It has a specificity of 91% and a sensitivity of 56%. Obesity, but not steatosis could interfere with the measurement of liver elasticity.

Although a liver biopsy may give very valuable information, it is not absolutely necessary to initiate antiviral treatment. Dr. Afdhal proposed an algorithm in which patients with HBV or HCV disease would undergo a non-invasive fibrosis test, and biopsy would be performed in patients with scores < F2 (or observe).

He concluded by saying that fibrosis markers and FibroScan® can stage liver disease as accurately as biopsy, and save up to 70% of patients a liver biopsy. Among future trends, he highlighted the need of performing longitudinal studies to assess the risk for disease progression with novel non-invasive techniques, of validating these non-invasive techniques and the MELD score in HIV+ patients, and of determining with prospective studies the role of combinations of non-invasive tests.

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