Detection of the hepatitis C virus

HCV in the material is normally absent.

Unlike serological methods for diagnosis of HCV where AT is detected to HCV, PCR allows detection of the presence of HCV RNA directly and quantitatively expressing its concentration in the

material under study. The test has specific specificity and high sensitivity: ten HCV RNA molecules in the test material are sufficient for its detection. Detection of AT to HCV confirms only the fact of infection of the patient, but does not allow to judge the activity of the infectious process( about the replication of the virus) and the prognosis of the disease. In addition, AT to HCV is found both in the blood of patients with acute and chronic hepatitis, and in those patients who have been ill and recovered, and often AT in the blood appear only a few months after the appearance of the clinical picture of the disease, which makes diagnosis difficult. Detection of HCV in the blood using PCR is a more informative diagnostic method. The detection of HCV RNA in PCR testifies to 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 in the early stages of the development of a viral infection against the background of the complete absence of any serological markers may serve as the earliest evidence of infection. However, the isolated detection of HCV RNA against the background of the complete absence of any other serological markers can not completely eliminate the false positive result of PCR.In such cases, a comprehensive evaluation of clinical, biochemical and morphological studies is necessary, with repeated repeated confirmation of the presence of PCR infection. The algorithm for diagnosing HCV using the PCR method is shown in Fig.

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

It is practically important for the detection of HCV RNA to investigate the PCR method not only with serum, but also with lymphocytes and hepatobiobaptam. Viruses can be detected 2-3 times more often in liver tissue than in serum. When evaluating the results of the study of blood serum for HCV RNA, it should be remembered that viremia can be fluctuating in nature( like the change in enzyme activity).Therefore, after positive results of the PCR study, a negative result can be obtained and vice versa. In such cases, to resolve the doubts that arise, it is better to investigate hepatobiobaths.

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

■ resolution of questionable results of serological studies;

■ differentiation of HCV from other forms of hepatitis;

■ detection of the acute stage of the disease in comparison with the transferred infection or contact;the stage of infection of newborns from seropositive HCV mothers;

■ monitoring the effectiveness of antiviral treatment.

All of the above features of the evaluation of results and approaches to the diagnosis of HCV using PCR are relevant to other infections.

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

■ increased activity of transaminases;

■ presence of HCV RNA in the blood;

■ genotype 1 HCV;

■ high viremia in the blood( more than 8x105 copies / ml).

It is now possible to quantitatively determine the HCV RNA content in the blood serum by PCR, which is of great importance for the management of interferon alpha treatment. The level of viremia is assessed as follows: for HCV RNA from 102 to 104 copies / ml - weak;from 105 to 107 copies / ml - medium, above 108 copies / ml - high. With effective treatment, the level of viremia decreases.