Approach to the Patient with Positive Hepatitis B Surface Antigen

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You answered:

The most appropriate blood test is a hepatitis B e antigen (HBeAg), which alone can determine if the patient is an inactive carrier of hepatitis B or if he is actively infected.

This answer is incorrect. HBeAg should be measured as part of the initial workup, but alone cannot determine if the patient has active hepatitis B infection. The presence of HBeAg indicates viral replication, and can be detected in persons with chronic active HBV infection as well as in those with acute infection. The exception is the patient with a precore mutant strain of hepatitis B virus, whose blood work will demonstrate a high HBV DNA level despite a negative HBeAg serologic test.

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	The next appropriate blood test is a hepatitis B core antibody (anti-HBc), which alone can determine if the patient has acute hepatitis B infection.
	No further blood work is necessary. The finding of positive HBsAg alone is enough to define the patient as a chronic hepatitis B carrier, and he should be screened for hepatocellular carcinoma with a serum alpha-fetoprotein measurement and abdominal ultrasound.
	Appropriate laboratory studies should include a complete hepatitis B serologic evaluation, a serum HBV DNA level, and biochemical markers related to hepatic inflammation and function.

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