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Old 01-29-2013
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Default Infectious dx question from MTB

MTB 2ck(2nd edition) page 19;

Which of the following indicates that a pxt is no longer a risk for transmitting HBV infection to another person?

a.bilirubin normalizes
b.No e-antigen found
c.No surface antigen found
d.No core IgM antibody found
e.ALT normalizes

I disagree with his answer.need your input guys
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Old 01-29-2013
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Quote:
Originally Posted by blade View Post
MTB 2ck(2nd edition) page 19;

Which of the following indicates that a pxt is no longer a risk for transmitting HBV infection to another person?

a.bilirubin normalizes
b.No e-antigen found
c.No surface antigen found
d.No core IgM antibody found
e.ALT normalizes

I disagree with his answer.need your input guys
I agree with you. His explanation is bunk for why C is the best answer. Med school and Step 1 said that if HbeAg is (+) = transmissible. I'm going to stick to that.
Here is my reasoning: I think that the question is worded poorly. it's asking two different things: 1) transmissibility and 2) if the infection is active
Transmisibilty correlates with HbeAg being (+)
if HbSAg is (+) = this indicates that the infection is still active. If it>6mo= means active chronic infection. that being said, obviously HbeAg (+) indicates that the infection is active too. "you cant have HbeAg (-) active infection"... correct?
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Old 01-29-2013
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Quote:
Originally Posted by USMLE234 View Post
I agree with you. His explanation is bunk for why C is the best answer. Med school and Step 1 said that if HbeAg is (+) = transmissible. I'm going to stick to that.
Here is my reasoning: I think that the question is worded poorly. it's asking two different things: 1) transmissibility and 2) if the infection is active
Transmisibilty correlates with HbeAg being (+)
if HbSAg is (+) = this indicates that the infection is still active. If it>6mo= means active chronic infection. that being said, obviously HbeAg (+) indicates that the infection is active too. "you cant have HbeAg (-) active infection"... correct?
Yeah....correct
Transmissible correlates with HBeAg and HBV DNA +ve.
It does not depend on the presence of surface antigen as he claims.

Thanx buddy....
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Old 01-29-2013
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you guys are mixing two things;

(+) e-antigen indicates increased risk of transmission, but (-) result does not mean the patient cant transmit it anymore. Only the risk is decreased

on the other hand, (-) HbsAg means the virus is no longer replicating, & thus the patient cannot transmit hepB, no matter how hard he tries.
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Quote:
Originally Posted by theundead View Post
you guys are mixing two things;

(+) e-antigen indicates increased risk of transmission, but (-) result does not mean the patient cant transmit it anymore. Only the risk is decreased

on the other hand, (-) HbsAg means the virus is no longer replicating, & thus the patient cannot transmit hepB, no matter how hard he tries.
Agree with you
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Old 01-29-2013
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Quote:
Originally Posted by theundead View Post
you guys are mixing two things;

(+) e-antigen indicates increased risk of transmission, but (-) result does not mean the patient cant transmit it anymore. Only the risk is decreased

on the other hand, (-) HbsAg means the virus is no longer replicating, & thus the patient cannot transmit hepB, no matter how hard he tries.
who is a chronic healthy career then??

my understanding & what i learnt from goljan step 1 audio;HBsAg presents 1st after HBV infection.pxt is never infective until HBeAg & HBV DNA are present.

in a healthy chronic career,the HBeAg and DNA have gone but HBsAg persists for longer than 6 months.these pxts have not recovered from the infection but they are not infective
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Old 01-29-2013
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Theundead is absolutely right. As long as the patient HBsAg positive he can transmit the disease. Presence of HBeAg indicates increased risk of this event. On the other hand absence of HBeAg does not exclude this possibility. Only disappearance of HBsAg indicates that the patient is cured and no longer represents danger to others.
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Quote:
Originally Posted by oxygen View Post
Theundead is absolutely right. As long as the patient HBsAg positive he can transmit the disease. Presence of HBeAg indicates increased risk of this event. On the other hand absence of HBeAg does not exclude this possibility. Only disappearance of HBsAg indicates that the patient is cured and no longer represents danger to others.

Can any one of you site your source pls???

This is what I copied from wiki

Main article: Hepatitis B virus
Structure


The structure of hepatitis B virus

The genome organisation of HBV. The genes overlap.
Hepatitis B virus (HBV) is a member of the Hepadnavirus family.[12] The virus particle, (virion) consists of an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. These virions are 42 nM in diameter and are sometimes referred to as "Dane particles".[25] The nucleocapsid encloses the viral DNA and a DNA polymerase that has reverse transcriptase activity.[13] The outer envelope contains embedded proteins that are involved in viral binding of, and entry into, susceptible cells. The virus is one of the smallest enveloped animal viruses, but pleomorphic forms exist, including filamentous and spherical bodies lacking a core. These particles are not infectious and are composed of the lipid and protein that forms part of the surface of the virion, which is called the surface antigen (HBsAg), and is produced in excess during the life cycle of the virus.[26]

You can google HBV transmission and read for yourself
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Old 01-30-2013
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Here's the source(s). hope this helps
Quote:
Hepatitis B e antigen
Presence indicates highly infective stage of Hepatitis B
Note:
1) May be negative in “pre-core mutant” form of Hepatitis B which is still
highly infective - further tests, such as HBV DNA, may need to be
performed to show high level on infectivity
http://www.qml.com.au/Files/Hep_Ser_485.pdf

Quote:
A positive result indicates the person has high levels of virus and greater infectiousness.
A negative result indicates low to zero levels of virus in the blood and a person is considered less infectious.
(note that it doesnt say non-infectious)
http://www.hepb.org/patients/additional_blood_tests.htm

I think you are mixing low infectivity with zero infectivity. CK is all about the subtle differences.


EDIT:
this one is a nice flash video of different hepB markers http://depts.washington.edu/hepstudy.../mainMovie.swf

Last edited by theundead; 01-30-2013 at 05:04 AM.
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Quote:
Originally Posted by blade View Post
These particles are not infectious and are composed of the lipid and protein that forms part of the surface of the virion, which is called the surface antigen (HBsAg), and is produced in excess during the life cycle of the virus.
This is absolutely true also . But only if these particles (HBsAg) were separated from the whole virion in the laboratory. Actually they are used for vaccination. But in the case of viral infection they simply indicate that the infection is still there. My source - all these USMLE books including Goljan. They all state that for example if pregnant women is HBsAg positive the risk of transmission of the hepatitis B to the baby is 10%, but if she both HBsAg and HBeAg positive this risk rises to 80-90%. The same way all these books recommend postexposure prophylaxis against hepatatis B in the case of contact with HBsAg positive blood and it doesn't metter whether this blood is HBeAg positive or not. I hope I convinced you .
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Old 01-30-2013
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Quote:
Originally Posted by USMLE234 View Post
I agree with you. His explanation is bunk for why C is the best answer. Med school and Step 1 said that if HbeAg is (+) = transmissible. I'm going to stick to that.
Here is my reasoning: I think that the question is worded poorly. it's asking two different things: 1) transmissibility and 2) if the infection is active
Transmisibilty correlates with HbeAg being (+)
if HbSAg is (+) = this indicates that the infection is still active. If it>6mo= means active chronic infection. that being said, obviously HbeAg (+) indicates that the infection is active too. "you cant have HbeAg (-) active infection"... correct?
I 100% agree with you.
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My 2 cents:

Both HBsAg (surface)& HBeAg (inner core) are part of the same virus.
So, it makes sense that both indicate infectivity.
However, it takes some time for HBeAg to appear in the serum (and, therefore, detectable by the test). During this period (HBsAg + & HBeAg -) the patient can still transmit the infection. Test for HBsAg does not tell you the quantity of the virus just the presence of it.

However, appearance of HBeAg means that patient is actively producing a lot of virus. The more quantity means more chances of transmission. Therefore, there is a very high risk of infection in the presence of HBeAg (HBsAg + & HBeAg +) as compared to HBsAg + & HBeAg - since there is a lot more of the virus to infect per unit volume (HBeAg+ = High Infectivity).

There cannot be a scenerio where HBsAg - & HBeAg + since the virus has to be alive and well to make HBeAg.

Hope this clears the confusion.
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Last edited by Novobiocin; 01-30-2013 at 08:13 AM.
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Quote:
Originally Posted by blade View Post
MTB 2ck(2nd edition) page 19;

Which of the following indicates that a pxt is no longer a risk for transmitting HBV infection to another person?

a.bilirubin normalizes
b.No e-antigen found
c.No surface antigen found
d.No core IgM antibody found
e.ALT normalizes

I disagree with his answer.need your input guys
So, based on above explanation C is the correct answer since there can be no e antigen without the presence of surface antigen.
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