Hepatitis C PCR

HCV is normally absent in the material.

Unlike serological methods of diagnosing viral hepatitis C, which detect antibodies to HCV, PCR allows to detect the presence of HCV RNA directly and to quantify its concentration in the test material. The test has species specificity and high sensitivity: ten HCV RNA molecules in the test material are enough to detect it. Detection of antibodies to HCV only confirms the fact of patient infection, but does not allow to judge the activity of the infectious process (replication of the virus) and the prognosis of the disease. In addition, antibodies to HCV are detected both in the blood of patients with acute and chronic hepatitis, and in those patients who were ill and recovered, and often antibodies in the blood appear only several months after the onset of the clinical picture of the disease, which complicates diagnosis. Detection of HCV in the blood using PCR is a more informative diagnostic method. Detection of HCV RNA in PCR indicates viremia, allows to judge the replication of the virus in the body and serves as one of the criteria for the effectiveness of antiviral therapy. Detection of HCV RNA by PCR at early stages of viral infection in the complete absence of any serological markers may serve as the earliest evidence of infection. However, isolated detection of HCV RNA in the complete absence of any other serological markers cannot completely exclude a false-positive PCR result. In such cases, a comprehensive assessment of clinical, biochemical and morphological studies with repeated multiple confirmation of the presence of infection by PCR is necessary.

The use of the PCR method in patients with chronic viral hepatitis C is of great importance, since most of them lack a correlation between the presence of viral replication and the activity of liver enzymes. In such cases, only PCR allows us to judge the presence of viral replication, especially if the final result is expressed quantitatively. In most cases of the disease, the disappearance of HCV RNA from the blood serum occurs later than the normalization of liver enzymes, so their normalization cannot serve as a basis for stopping antiviral treatment.

It is practically important to examine not only blood serum, but also lymphocytes and hepatobiopsy specimens using the PCR method to detect HCV RNA. Viruses can be detected 2-3 times more often in liver tissue than in blood serum. When evaluating the results of a blood serum test for HCV RNA, it should be remembered that viremia can be fluctuating in nature (as well as changes in enzyme activity). Therefore, after positive PCR test results, a negative result can be obtained and vice versa. In such cases, it is better to examine hepatobiopsy specimens to resolve any doubts that arise.

Detection of HCV RNA in material using PCR is used for the following purposes:

• resolution of questionable serological test results;
• differentiation of viral hepatitis C from other forms of hepatitis;
• identification of the acute stage of the disease in comparison with the previous infection or contact; determination of the stage of infection of newborns from HCV-seropositive mothers;
• monitoring the effectiveness of antiviral treatment.

Patients with suspected viral hepatitis C:

• donors;
• persons with risk factors;
• individuals with elevated ALT activity;
• patients with acute hepatitis

All the above-mentioned features of the evaluation of results and approaches to the diagnosis of HCV using PCR also apply to other infections.

The PCR method allows not only to detect HCV RNA in the material being studied, but also to establish its genotype. Determination of the virus genotype is of great importance for the selection of patients with chronic viral hepatitis C for treatment with interferon-alpha and ribavirin. Laboratory indications for the treatment of chronic viral hepatitis C with interferon alpha are as follows:

• increased transaminase activity;
• presence of HCV RNA in the blood;
• HCV genotype 1;
• high viremia in the blood (more than 8×10 ⁵ copies/ml).

Currently, it is possible to quantitatively determine the HCV RNA content in blood serum using the PCR method, which is of great importance for monitoring interferon alpha treatment. The level of viremia is assessed as follows: with HCV RNA content from 10 ² to 10 ⁴ copies/ml - weak; from 10 ⁵ to 10 ⁷ copies/ml - average, above 10 ⁸ copies/ml - high. With effective treatment, the level of viremia decreases.

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