What is the diagnosis of Dengue?

By  , Expert Content
Apr 04, 2011

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Remember that people of all age and sex can be affected by dengue fever. Deaths and complication of dengue occur more frequently in children during Dengue Fever outbreak.


Clinical diagnosis of dengue fever can be difficult. The signs and symptoms of dengue fever are similar to several diseases like flu, malaria, and typhoid fever. To confirm the diagnosis your doctor will test your blood for presence of dengue virus or antibodies to dengue virus.


Blood tests: Tests done to confirm a diagnosis of dengue fever are:

  • Test for virus: The dengue virus can be identified from serum or autopsy tissue samples. Reverse transcriptase-polymerase chain reaction (RT-PCR) test is used to identify dengue virus.
  • Test for dengue antigens.
  • Test for antibodies: The Dengue ELISA test is done to test for IgG and IgM antibodies to dengue virus.


Your antibody response

Infection with any type of dengue virus results in lifelong immunity to that serotype, but only temporary immunity to other serotypes.


Primary Infection: First infection with any serotype results in formation of IgM and IgG antibodies

  • The IgM antibodies are detected in blood tests approximately 5 days after the symptoms of dengue fever start. These antibodies continue to rise for the next 1-3 weeks  and are detected for up to 6 months
  • IgG antibodies are detected in blood tests approximately 14 days after the symptoms of dengue fever start and are maintained for life

Secondary Infection: Second infection with any serotype

  • IgM antibodies are not formed in approximately 5% patients
  • IgM titer may increase slowly in secondary infection
  • IgG antibodies are detected approximately 2 days after symptoms start and are significantly higher as compared to primary infection


What is the "Platelet count with dengue" virus?

The dengue virus can affect the platelet production in some patients. The normal life span of platelets is about 4 days and the normal platelet count is 1.5 to 4.5 lakhs. The virus affects the body's ability to form new platelets and the number of platelet decrease (decrease in platelet count is called thrombocytopenia). Platelets are needed to form blood clot. Decrease in platelet count affects the body's ability to form blood clot. Decrease in platelet count (thrombocytopenia) increases the risk of hemorrhage or bleeding. The bleeding can be both internal & external. Your doctor may recommend platelet transfusion if the platelet counts decrease below is 20,000-25,000/mm3 or if you have bleeding even if the count is higher.


Other blood cell counts in dengue:

  • Total White Blood Cells Count: In some people with dengue, the white blood cell count can decrease (leucopenia). If the white blood cell count is high the possibility that you have dengue decreases and bacterial infection must be considered.
  • Hematocrit (micro-hematocrit): In DHF patients the blood becomes thicker or there is hemoconcentration (that is the hematocrit is elevated >20% for age and sex). If the hematocrit before infection is not known hematocrit > 45% is regarded as significant.


Read more articles on Dengue Diagnosis and Prognosis


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