The diagnosis is confirmed when the patient has clinical and laboratory findings of acute hepatitis plus a positive HBsAg. However, in some patients with acute hepatitis B, their blood can be undetectable for HBsAg (HBsAg has been negative or the test is not sensitive), and for such patients we must rely on other indicators than HBsAg. Second, asymptomatic hepatitis B surface antigen carriers are quite common in China. These patients who are combined with other types of acute hepatitis (such as hepatitis A, hepatitis C, EBV or CMV viral hepatitis, toxic hepatitis, etc.) are easily misdiagnosed as acute hepatitis B because their blood is positive for HBsAg, and it is sometimes very difficult to distinguish such patients from true acute hepatitis B. How to diagnose a patient with acute hepatitis is generally not very difficult, especially for acute jaundiced hepatitis: acute onset; sudden onset of significant fatigue and weakness and significant gastrointestinal symptoms with no other explanation; jaundice after about a month; mild to moderate enlargement of the liver with pressure pain; very high serum ALT values. The jaundice-free type sometimes has no obvious symptoms or signs, but if the onset is indeed acute, with gastrointestinal symptoms and hepatomegaly and very high ALT, it is usually not very difficult. It is generally believed that the presence of hepatitis B virus in the patient’s body can be confirmed based on the following points: ① HBsAg positivity. ② Positive anti-HBcIgM antibody, especially when the potency is very high, often represents the presence of hepatitis B virus in the patient’s body. ③Significant elevation of DNA polymorphic enzyme activity or positive e antigen. The presence of Dane particles in the blood or HBsAg or HBcAg in the liver biopsy tissue also indicates the presence of virus in the body. To determine that the patient’s acute hepatitis is indeed caused by the hepatitis B virus and not a carrier of the hepatitis B virus with another cause of acute hepatitis. Generally, this can be based on the following points: (1) Double serum in the acute and recovery periods, the hepatitis B surface antibody (anti-HBs) changes from negative to positive or the titer increases fourfold or more. ② Double serum in the acute and recovery periods, with more than 4-fold increase in hepatitis B core antibody (anti-HBc).