A 5 year old boy has been having fever for 2 days. Dengue IgM and IgG were requested and revealed: IgM = negative
IgG = positive
Question: Can you conclude from the result that the patient has dengue? Can you conclude from the result that the patient does not have dengue at the moment? Explain your answer.
Dengue is a viral infection transmitted by mosquitoes in tropical areas. In medical prognosis or diagnosis, a primary dengue infection results in detectable levels of IgM antibodies by the 3rd afebrile day after infection, which generally persist for 2-6 months. Dengue IgG antibodies appear after IgM, approximately at the day 7 of the fever in the primary infection and persist for a longer time, even up to years. Secondary Dengue infections are characterized by a rapid increase in IgG levels, with modest increases in IgM.
From the above case of the 5 year old boy, the IgG is positive but the IgM is low or negative, then it is likely that the patient had an infection sometime in the past. Conclusively; presence of IgG alone (absence of NS1 Ag and/or IgM), does not indicate active dengue infection.