Anonymous asked in HealthDiseases & ConditionsInfectious Diseases · 1 month ago

How is it possible to have a negative total core antibody, but a positive IgM antibody for hepatitis B testing?

All other tests were negative including HbsAg and HBV DNA. Patient had 3 vaccinations as a child and only one small risk factor of unprotected sex with one person.


Since total core antibodies includes both IgM and IgG, how could that have shown up negative, and then a separate IgM test become positive? 

Update 2:

Liver function tests were normal with no symptoms.

1 Answer

  • 1 month ago
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    Appropriate test at the right time increases the positive and negative predictor of lab tests and reduces the false negatives and false positives. 

    The antibody test IgM anti-HBc is included in the hepatitis panel because it is useful in detecting hepatitis B in those patients showing hepatitis ie elevated liver enzymes along with clinical hepatitis. If you don't have that then you don't have hepatitis. You just increased your chances of having false positive testing. 

    The total anti-HBc test as mentioned detects both IgM and IgG antibodies. There is no test that solely detects IgG. That test should have been positive to confirm the other test as stated. It did not and so one is left with one or the other as being inaccurate. 

    The surface antigen is negative and more importantly the PCR was negative which confirms that no active infection is present. 

    You make no mention of hepatitis B surface antibody testing which should be positive because of immunization or through past infections. No mention of hepatitis E antigen and antibody status. 

    Each test IgM and total core antibody tests are separate entities which may even by manufactured by different companies with different antibody preparations differing in reactivity and differing in outside interference with regards to biologicals. 

    It is a known fact that false positives with regards to rheumatoid arthritis, HIV status and biotin intake can create test interference. If it was only slightly positive then I would not worry about it but if indeed it is persistent then I would search for causes that might impact future health. The question with regards to hepatitis has been answered but the cause of the false positive is still unanswered. Repeat testing of IgM would be in order to make sure it is consistent and not a lab error such as clerical data or identity or contamination that one time. 


    The patient with negative HBsAb doesn't necessarily mean that the vaccine did not take. Much has been made to confirm whether or  not the vaccine took was to re-challenge with the vaccine and see if one gets an amnestic response which takes off to high antibody numbers after a week or so. An antibody can disappear over time but that doesn't mean that the vaccine was or is ineffective. There used to be boosters for HBV vaccine but no longer recommended based on those facts.  There is no present nor past infection with regards to HBV. It might be to their benefit if an RA test were done along with HIV serology and ask supplement history if the patient was taking biotin. I think it is a worthwhile endeavor considering RF factor can interfere with lots of laboratory tests along with biotin. The interference can cause false negative and false positive tests some of which can be critical. 

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