As many patients know, hepatitis B examination items mainly include liver function test, hepatitis B two-and-a-half test, HBV-DNA test, ultrasound test, etc. HBV-DNA test, as one of the hepatitis B examination items, is a mandatory item for regular review of hepatitis B patients, but many people know that HBV-DNA should be checked, but they do not know what is the purpose of HBV-DNA test and what is the use of checking HBV-DNA. What is HBV-DNA? What is HBV-DNA? HBV stands for hepatitis B virus and DNA stands for deoxyribonucleic acid. HBV-DNA is the most direct, specific and sensitive indicator of HBV infection, and a positive HBV-DNA indicates that HBV is replicating and infectious. the higher the HBV-DNA, the more viral replication and infectious it is. What is the purpose of HBV-DNA test? 1, the prognosis of HBV carriers assessment Check the results, if HBeAg and HBVDNA are negative, and the serum ALT is normal, known as chronic hepatitis B surface antigen carriers, the disease progresses slowly or tends to be stationary, the prognosis is good, generally do not need drug treatment; if HBeAg and HBV DNA positive, or HBeAg negative, but HBVDNA positive, known as HBV carriers, prone to recurrent liver inflammation episodes, faster disease progression and poorer prognosis generally require treatment or intervention, but need to be combined with liver biopsy histological examination, imaging examination and other comprehensive assessment. 2.Discovery of occult hepatitis B cases The screening of HBV infection is defective, mainly based on HBsAg or hepatitis B two-to-one examination, which cannot detect occult hepatitis B with negative HBsAg, and the determination of HBV DNA makes the diagnosis more accurate. 3, grasp the indications for treatment, evaluation of antiviral efficacy Hepatitis B antiviral guidelines have taken the quantification of viral DNA as one of the key indicators to assess the need for antiviral therapy, and different requirements have been made for the quantification of viral DNA in patients with “major three yang” and “minor three yang”. In the process of anti-hepatitis B virus treatment, the decrease of viral DNA quantification is one of the main indicators to evaluate the efficacy. 4, to ensure the safety of the blood source If only the requirement of blood donors with negative surface antigen and normal serum ALT can not detect the occult hepatitis B virus infection, window period virus infection can not be detected, the HBV DNA quantification needs to be checked at the same time to further ensure the safety of the blood source.