Hepatitis B e antigen in serum indicates
Answer: A
The e antigen is produced during vigorous replication, so its presence marks a highly infectious phase, which matters greatly in pregnancy and after a needlestick. Its loss and the appearance of anti-HBe usually mark a fall in replication.
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The window period in hepatitis B serology is the interval when
Answer: B
Between the disappearance of the surface antigen and the appearance of its antibody, core antibody is the only positive marker, so testing for surface antigen and its antibody alone can wrongly suggest no infection. Including anti-HBc is what closes the gap.
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A person with surface antigen persisting beyond six months is regarded as having
Answer: C
Correct answer: chronic hepatitis B infection
Six months is the conventional dividing line. Surface antigen still present after that means the infection has not been cleared and is now chronic, with a lifetime risk of cirrhosis and hepatocellular carcinoma that requires monitoring. Its disappearance within six months marks resolution.
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The hepatitis B vaccine contains
Answer: D
Yeast cells engineered to make the surface antigen supply the vaccine, so it contains no viral nucleic acid and cannot cause infection. The response it raises is anti-HBs alone, which is why the vaccinated lack core antibody.
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Hepatitis B immune globulin differs from the vaccine in that it provides
Answer: A
Ready-made antibody acts at once and is used after a needlestick or for a newborn of an infected mother, usually together with the first dose of vaccine. The protection wanes within months, whereas the vaccine builds lasting immunity.
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Which family, related to the yellow fever and dengue viruses, contains hepatitis C?
Answer: B
It is an enveloped virus with a positive-sense single-stranded RNA genome, related to the yellow fever and dengue viruses. Its high mutation rate produces the quasispecies diversity that has frustrated vaccine development.
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Hepatitis C is transmitted chiefly by
Answer: C
Sharing needles, syringes or other injecting equipment accounts for most transmission, with childbirth, sexual contact and unregulated tattooing far less common. Blood transfusion was a major route before donor screening.
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The proportion of people infected with hepatitis C who develop chronic infection is
Answer: D
Fewer than half clear the virus without treatment, so most acute infections become chronic, which is the opposite of the pattern in adult hepatitis B. Chronicity combined with a silent early course is what made hepatitis C such a large reservoir of undiagnosed liver disease.
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Cirrhosis develops in hepatitis C in about
Answer: A
Correct answer: 5 to 25 per cent over 10 to 20 years
Hepatitis C is slow. Most acute infections become chronic, and of those a minority progress to cirrhosis over one or two decades - faster where alcohol, obesity or coinfection are present. The long silent interval is why so many infections were found only when the liver disease appeared, and why screening rather than symptoms identifies them.
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A patient with hepatitis C cirrhosis carries an annual risk of hepatocellular carcinoma of about
Answer: B
Once cirrhosis is established the yearly risk of liver cancer is appreciable, which is why such patients are enrolled in regular surveillance with imaging. The risk arises from the cirrhosis rather than from the virus acting directly.
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