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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Antigen which does not appear in blood in hepatitis B:
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The correct answer is  Because HBcAg is intracellular and, when in the serum, sequestered within an HBsAg coat, naked core paicles do not circulate in serum and, therefore, HBcAg is not detectable routinely in the serum of patients with HBV infection. By contrast, anti-HBc is readily demonstrable in serum, beginning within the first 1-2 weeks after the appearance of HBsAg and preceding detectable levels of anti-HBs by weeks to months.