Have a patient currently being managed for both, Dengue fever, and Typhoid fever. Wanted to know if either one of the two reports could be a false positive. Kindly cite references for the same, if possible. Thank you !
If you are asking if they cross react I am not aware of that. However, depending on the part of the world you are in and the current or past vaccination, immunological history, and viral exposure you could see false positives for dengue. The lower you go on the titters the more likely the positive result is false. In part this is why we usually ask for titters several weeks apart since it allows for temporary fluctuations. In addition there are numerous Flavivirus species related to dengue that cross react especially at low titters. This is the eternal problem with serology. It only tells you that antibodies are reacting to an antigen and not that they are most reactive to that antigen compared to something that you did not test such as Zika, West Nile, etc.
Thank you will. The patient is in Mumbai currently. This is a part where other flaviviruses aren't common. Japanese Encephalitis occurs in the northeast, but not this part of India. Neither is kyasanur forest disease, which occurs way south. We anyways starte
I think the serology of typhoid fever is not an easy task and facing many practical points e.g false positive results
In Asia there is always the possibility the patient has a double infection.
Dear Bruce Arthur Harrison
The situation in Africa now is not different form the one in Asia
May I know which test for dengue was positive. Widal is a non specific test for diagnosis of typhoid fever. However rising titre in the subsequent sample may be considered if the disease is strongly suspected. Blood culture is the gold standard for diagnosis of typhoid fever
This could be case of co- infection of Dengue + Typhoid . The major problem for the clinician is analyzing the reports . For eg. It could mean that the patient had typhoid in the past & Dengue at present with anamestic rise of widal titres . It is preferable to look for features such as thrombocytopenia for dengue & splenomegaly for typhoid . It is preferable to treat both ,as the patient's health is more important than to take a risk in not treating . It should be explained to the patient the rationale behind treatment or questions will be raised about the validity of the tests on why we did these tests , if we do not trust the reports .
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