October 17, 2010

PLAB Question 11

A young man develops acute hepatitis B. Four months after his presentation he asks for a test that would predict the likelihood of developing long term disease.

Which agent would be most helpful in estimating the likelihood of developing chronic active hepatitis in this patient?

a) recombinant hepatitis B vaccine
b) hepatitis C virus
c) Hepatitis B surface antigen
d) hepatitis C vaccine
e) hepatitis D
f) hepatitis B immune globulin (HBIG)
g) hepatitis B virus DNA
h) hepatitis B e antigen
i) hepatitis A
j) atopic dermatitis

The correct answer is H

Hepatitis B e antigen (HBeAg) is a product of the gene that codes for the nucleocapsid core; its presence signifies the presence of a state of high virus replication. As such, patients with HBeAg have a high level of circulating virions, high infectivity, and substantial liver injury.

HBeAg becomes detectable in all patients early during acute hepatitis B, and, therefore, there is no clinical utility to the test during early acute hepatitis B; however, if circulating HBeAg persists beyond the first 3 months of acute hepatitis, the likelihood of chronic infection is increased.

Testing for HBeAg is more important during chronic infection, for the presence of HBeAg denotes a more highly replicative chronic infection, associated with increased infectivity (eg, 20-25% infectivity of a needlestick) and liver injury (eg, chronic active hepatitis).

When anti-HBe can be detected in the absence of HBeAg during chronic infection, the patient can be classified as having a less replicative infection, with limited infectivity (eg, 0.1% infectivity of a needlestick) and liver injury (chronic carrier).

Hepatitis B virus DNA (HBV DNA) is a more quantitative marker of HBV replication, and is helpful in following patients with chronic disease and in monitoring the success of antiviral therapy

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