Hepatitis B, Hepatitis C, Hepatitis D... Understand the detection of viral hepatitis in one article

Author: Lou Jinli, researcher/professor at Beijing You'an Hospital, Capital Medical University

Reviewer: Wang Lixiang, Chief Physician, Third Medical Center, PLA General Hospital

The 10th Chairman of the Science Popularization Branch of the Chinese Medical Association

In the medical field, viral hepatitis is a common infectious disease, and its diagnosis and treatment have always attracted much attention. With the continuous advancement of medical technology, the detection methods for viral hepatitis are becoming increasingly accurate and diversified.

Detection of HBV-DNA using PCR technology can be used as direct evidence of hepatitis B virus (HBV) infection. When HBV-DNA is positive, it means that the patient has been infected with the hepatitis B virus and the virus is in a state of replication. It is worth noting that the value of HBV-DNA does not directly reflect the severity of the disease. For example, during the immune tolerance period, although the virus replication is very high, the liver cells are not damaged and the liver function remains normal. Therefore, the value of HBV-DNA can only be used as a reference for the state of viral replication, rather than a basis for judging the severity of the disease.

HBV-DNA testing plays an important role in the clinical treatment of hepatitis B. First, before treatment, it can help doctors understand the replication status of the virus in the patient's body and provide baseline data for formulating treatment plans. Secondly, during the treatment process, the efficacy of the drug can be evaluated by monitoring the changes in HBV-DNA. If the HBV-DNA value drops significantly, it means that the treatment is effective; conversely, if the value drops first and then rises, the virus may have developed drug resistance and the treatment plan needs to be adjusted in time. Finally, at the end of treatment, HBV-DNA testing can also serve as an important basis for whether to stop the drug. Only when HBV-DNA is not detected and after a period of monitoring, can you consider stopping the drug.

Figure 1 Original copyright image, no permission to reprint

However, the detection of HBV-DNA is not static. With the continuous advancement of detection technology, ultra-sensitive nucleic acid detection has emerged. It uses more sensitive reagents and can detect lower concentrations of viral nucleic acids. Ultra-sensitive nucleic acid detection not only improves the accuracy of detection, but also provides the possibility for the diagnosis of latent HBV virus infection. In addition, ultra-sensitive nucleic acid detection also provides a more reliable basis for issues such as the reactivation of the virus in immunocompromised patients and when to start antiviral treatment.

It is worth noting that even if the HBV-DNA test result is negative, it does not mean that the possibility of HBV infection is completely ruled out. For example, in the five hepatitis B tests, if the surface antigen (HBsAg) is positive and the HBV-DNA test result is negative, this may indicate that the virus is in an inactive replication state and the patient may be an inactive HBV carrier. In addition, this situation may also occur in the recovery stage after antiviral treatment or at a certain period during the natural infection process. Therefore, in the face of such situations, doctors need to comprehensively consider the patient's clinical manifestations and other laboratory test results to develop a reasonable follow-up plan.

In addition to HBV-DNA testing, another biomarker called pre-S1 antigen is also of great value. Pre-S1 antigen is part of the HBV envelope protein and is closely related to viral infection, replication, and induction of host immune response. Compared with traditional serological markers, pre-S1 antigen can reflect the status of HBV infection earlier and is especially suitable for early diagnosis of acute infection. Studies have shown that in patients with acute HBV infection, the rapid disappearance of pre-S1 antigen often indicates a good treatment prospect; conversely, if the pre-S1 antigen remains positive, it indicates that the infection may develop into a chronic state.

Figure 2 Original copyright image, no permission to reprint

Among viral hepatitis, in addition to hepatitis B, hepatitis A, hepatitis C, hepatitis D and hepatitis E are also worthy of attention. Serological testing is the main means of diagnosing hepatitis A and hepatitis E. By testing anti-hepatitis A virus IgM antibodies and anti-hepatitis E virus IgM antibodies, it can be determined whether the patient is newly infected. At the same time, combined with the detection of IgG antibodies, it can also be understood whether the patient has been infected with the virus and the current immune status.

The diagnosis of hepatitis C is more complicated. In addition to antibody testing, HCV-RNA testing is also required. HCV antibodies can be used as a screening test, and HCV-RNA testing can be used as a confirmatory test. Quantitative testing of HCV-RNA can not only determine whether the patient is currently infected, but also evaluate the replication activity of the virus and the efficacy of the drug. If the HCV antibody is positive, there may be a false positive or the virus has been cleared but the antibody persists; if the HCV antibody is negative, it may also be in the window period or the patient is immunocompromised or immunodeficient. Therefore, the diagnosis of hepatitis C should be based on a comprehensive judgment based on the results of HCV antibodies and RNA.

The diagnosis of hepatitis D is relatively special. Since the hepatitis D virus is often overlapped with the hepatitis B virus, it is necessary to perform an antigen-antibody test for the hepatitis B virus at the same time as the hepatitis D virus antibody test. Only when both are positive can the hepatitis D virus infection be confirmed.