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Gastroenterol Clin Biol. 2005 May;29(5):573-6.

Usefulness of specific IgG avidity for diagnosis of hepatitis A infection.

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Centre National de Référence pour les virus à transmission entérique, Laboratoire de Virologie, Hôpital Paul Brousse, Villejuif.



Diagnosis of acute hepatitis A virus (HAV) infection is classically based on the detection of HAV-IgM. Nevertheless, HAV-IgM can be positive for patients with polyclonal stimulation of their immune system (i.e. immune reactivation). To improve the diagnostic yield, an avidity test for HAV-IgG antibodies was developed and tested.


Avidity tests were performed in 128 sera: 11 selected samples from patients with past infection, 15 acute hepatitis A, 10 vaccinated subjects and 4 patients with immune reactivation as well as 84 HAV-IgM positive unselected sera, provided by routine laboratories.


Patients with past infection had avidities over 70%, whereas avidities in patients with acute hepatitis A were below 50% during the first month following the onset of symptoms. As expected, patients with immune reactivation had avidities over 70% consistent with past infection. The results obtained for the 84 unselected sera allowed reconsidering the diagnosis of acute hepatitis A for nearly a third of patients.


This test could improve the diagnosis of acute hepatitis A infection, particularly in elderly patients.

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