Hepatitis C virus viraemia in HIV-positive individuals with negative HCV antibody tests
Sanjay Bhagani, HIV i-Base
This prospective study looked at the presence of hepatitis C virus viraemia (HCV RNA) in HIV-infected, HCV-antibody negative patients using an ‘in-house’ whole blood RT-PCR test for HCV RNA. A group of HIV-negative diabetic patients were used as controls. Samples from viraemic patients were then retested using commercially available plasma and serum HCV RNA tests.
Of the 100 HIV-positive, HCV-antibody negative patients, 20 (20%) had HCV RNA detected by the whole blood assay. None of the 100 HIV-negative, HCV-antibody negative controls had evidence of HCV viraemia (p <0.001). Of the 20, whole blood HCV viraemic patients, 16 were confirmed positive by RT-PCR on a previously obtained serum specimen. Eleven of the 20 patients had further confirmation of the viraemia by amplification and detection using primers from the NS5A region of the genome. Thus 19% of the HCV-antibody negative patients tested HCV RNA positive on two separate sample dates. Using a commercial RT-PCR (Roche Amplicor), six of the 20 patients had RNA detected in plasma using a standard method, and a further three were additionally positive using higher volumes of whole blood in the Roche assay. Therefore only 9% of the HCV-antibody negative population were HCV viraemic by commercially available RT-PCR.
Only one of these patients had a measurable HCV RNA concentration in the quantitative Roche Monitor 2.0 assay, indicating that these patients had low concentrations of HCV RNA present in plasma. By testing for HCV RNA in the earliest plasma or serum specimen available, the mean duration of HCV viraemia was found to be 26.8 months. HCV antibody was negative when repeated on the most recent plasma specimen in these 20 patients thus excluding recent infection with delayed seroconversion.
When demographic risk factors for acquisition of HCV and HIV were compared, HCV-antibody positive, HCV RNA positive patients were more likely to have a history of parenteral exposure than the 20 HCV viraemic seronegative patients (p <0.001). The parenterally exposed group had a significantly higher mean ALT (87 m/l vs. 38 m/l, p = 0.013) and non-significantly higher initial CD4 counts (211 cells/mm3 vs. 211 cells/mm3, p=0.125) than those who acquired HIV sexually.
The authors conclude that whole blood testing for HCV RNA demonstrates a significantly higher rate of HCV infection among patients with HIV infection who are HCV antibody negative. Furthermore, their whole blood in-house RT-PCR assay performed better than a standard commercial assay or a modification of the commercial assay. Although progression of liver disease was not evaluated in their study, they suggest that if the liver biopsy demonstrates significant fibrosis, then HCV therapy should be instituted, and abstinence from alcohol should be encouraged in these patients.
George SL, Gebhardt J, Klinzman D et al. Hepatitis C virus viremia in HIV-infected individuals with negative HCV antibody tests. J Acquir Immune Defic Syndr 2002 Oct 1;31(2):154-62
This study demonstrates the significance of HCV RT-PCR in the diagnosis of HCV in immunosuppressed patients who are HCV antibody negative. Other studies have demonstrated that up to 5% of HIV positive patients with HCV infection may not have detectable circulating HCV antibodies (measured by the commercially available ELISA tests). Current practice in most HIV units is where there is a high index of suspicion of HCV co-infection (unexplained elevated hepatic transaminases, extrahepatic manifestations of HCV), and in the absence of HCV-antibodies, an HCV RT-PCR test should be performed on serum or plasma.
In this study, the in-house whole blood RT-PCR picked up 50% more HCV infections than commercially available HCV PCR tests. The increased sensitivity of the whole blood assay, as compared to plasma or serum assays, can probably be explained by reservoirs of HCV in peripheral blood lymphocytes. However, all these patients have very low circulating HCV levels and the clinical significance (either in terms of liver disease progression, or HCV transmission) of this infection has yet to be demonstrated. Of course, lifestyle changes to minimise HCV related liver damage can be made earlier as a result of a more sensitive test.
It is likely that once HCV viral loads increase (and they do significantly in HIV co-infection over time), commercially available RT-PCRs will detect viraemia. Many of these patients, because of the immune defect, may not mount a detectable antibody response.
Although, whole blood HCV RT-PCR tests may be more sensitive in detecting viraemia in HCV antibody negative patients, their use in clinical practice is yet to be determined. For now, commercially available HCV PCR tests remain important diagnostic tools in immune suppressed HCV antibody negative patients.