HBV-DNA refers to the hepatitis B virus gene. Higher HBV-DNA indicates more viral replication and high infectivity. Medically HBV-DNA is equivalent to intact hepatitis B virus particles. The naked DNA (no protein-coated DNA) of the hepatitis B virus is infectious and completes the invasion of the host, causing the presence of intact hepatitis B virus particles in the host. The quantitative examination of hepatitis B virus DNA can not only understand the number of viruses in the patient’s body and the problem of the strength of infectivity, but also assess the effectiveness of treatment based on the results of the test. 1, HBV-DNA qualitative examination “+”: positive, the presence of virus replication in the body. Corresponds to HBV-DNA > 1x10E3 copies/ml in quantitative mode. “-“: negative, the degree of virus replication is below the detection limit. Corresponds to HBV-DNA < 1x10E3 copies/ml in quantitative mode. 2, HBV-DNA quantitative test HBV-DNA quantitative unit is usually expressed in the report form as "copies/ml", "copies/ml" or "IV/ml", which indicates the number of viral genomes per ml of serum or plasma, for example, "HBV-DNA=4.3 For example, "HBV-DNA=4.3 x 10E3 copies/ml" means there are 4.3 times 103 times or 4300 hepatitis B viruses in each ml of serum. a x 10Eb copies/ml The main way to judge the viral content in serum or plasma is to look at the "b" in the above equation, the larger the b, the higher the content. During the course of treatment, b becomes smaller, indicating that the replication of the virus is under control and the treatment is effective. Usually, if the virus level drops to b < 3, the virus is basically under control; if the virus level drops to "0", the virus is not present in the serum or plasma.