Laboratory Diagnosis of Dengue Viral Infection

Last updated on June 2nd, 2021

Dengue/dengue hemorrhagic fever (DHF) is a mosquito-borne viral disease caused by dengue virus, an Arbovirus (arthropod-borne virus). It is transmitted via the bite of an infected female Aedes aegypti mosquito. Laboratory diagnosis method for confirming dengue viral infection involves the use of one or a combination of any of the following four different methods 

  1. Microscopy and staining
  2. Culture
  3. Serology
  4. Molecular diagnosis

Note: These diagnosis methods are used for the diagnosis of any infections (viral, bacterial, parasitic, or fungal). The relative importance of a particular method differs among infections. Students are expected to know the main diagnostic test(s) of the particular infection.

Sample

  1. Early stages of the disease: after the onset of illness, the virus can be detected in blood (serum, plasma) or tissues; methods employed are; virus isolation, nucleic acid, or antigen detection.
  2. At the end of an acute phase of infection: serology is the method of choice.

Note: For virus culture, it is important to keep blood samples cooled or frozen to preserve the viability of the virus during transport from the patient to the laboratory.

Available methods for the diagnosis of Dengue Viral Infection
Fig 1: Comparison of dengue virus diagnostic tests according to their accessibility and confidence
  1. Microscopy and staining:  Direct visualization of the virus in the sample (using electron microscopy or via fluorescent staining technique) can be done. This is not the preferred method in diagnostic laboratories.
  2. Culture: Virus isolation in cell culture is difficult and is not the commonly used method in diagnostic laboratories because it is a demanding procedure (both in terms of infrastructure and technical expertise). Virus may be recovered from serum, plasma, and peripheral blood mononuclear cells. Inoculation of a mosquito cell line with patient serum, coupled with nucleic acid assays to identify the recovered virus is a commonly used approach in the research lab.
Fig 2: Approximate time-line of primary and secondary dengue virus infections and the diagnostic methods that can be used to detect infection
Fig 2: Approximate time-line of primary and secondary dengue virus infections and the diagnostic methods that can be used to detect infection

Serological test: Serological tests are the mainstay in the diagnosis of viral infections. 

  • Detection of viral antigen:
    • Dengue NS1 antigen detection is useful for the diagnosis of acute dengue infections up to 0-7 days of symptoms but not recommended after 7 days.
    • NS1 antigen has been detected in the serum of DENV infected patients as early as 1-day post-onset of symptoms (DPO), and up to 18 DPO.
    • NS1 ELISA based antigen assay is commercially available
    • NS1 assay may also be useful for differential diagnostics between flaviviruses because of the specificity of the assay.
  • Result interpretation 
    • A positive NS1 test result confirms dengue virus infection but does not provide serotype information.
    • A negative NS1 test result does not rule out infection. People with negative NS1 results should be tested for the presence of dengue IgM antibodies to determine possible recent dengue exposure.

Detection of anti-dengue antibodies in serum or other body fluids by ELISA or other rapid tests.  Various methods (IgM/IgG ELISA, Hemagglutination Inhibition Test, or rapid diagnostic kits) are available to detect anti-dengue antibodies; IgM detection:  

  • Useful for the diagnosis of primary dengue infection and in distinguishing dengue from other flavivirus infections.
  • IgM antibodies are detectable in 99% of patients by day 10 after the onset of illness.
  • IgM levels peak about two weeks after the onset of symptoms and then decline to undetectable levels over 2–3 months. 
  • Sensitivity: 65-75% sensitive in a single acute serum sample.
Rapid ICT based Test for the diagnosis of Dengue Infection
Fig 3: Rapid ICT based Test for the diagnosis of Dengue Infection

IgG detection: Tests that detect IgG are useful in diagnosing secondary disease (IgG is the dominant immunoglobulin type in secondary infection). The test is complicated by cross-reactivity of IgG antibodies to heterologous flavivirus antigens (West Nile virus, tick-borne encephalitis virus, yellow fever virus, zika virus).
Note: To distinguish between primary and secondary dengue infections, IgM/IgG antibody ratios are now more commonly used than the hemagglutination-inhibition test (HI).

  1. Molecular diagnosis:   detection of viral RNA in plasma or serum or tissues using nucleic acid amplification test (NAAT).  RT-PCR based methods for rapid identification and serotyping of dengue virus in acute phase serum are available.
Summary of operating characteristics and comparative costs of dengue diagnostic methods
Fig 4: Summary of operating characteristics and comparative costs of dengue diagnostic methods

Interpretation of Dengue Diagnostic Tests:

Highly SuggestiveConfirmed
One of the following:
  1.  IgM + in a single serum sample
  2. IgG + in a single serum sample with a HI titre of 1280 or greater
One of the following:
  1. PCR +
  2. Virus culture +
  3. IgM seroconversion in paired sera
  4. IgG seroconversion in paired sera or fourfold IgG titer increase in paired sera

References and Further Readings:

  1. WHO: Dengue Guidelines for Diagnosis, Treatment, Prevention and Control
  2. CDC: http://www.cdc.gov/dengue/clinicalLab/laboratory.html
About Acharya Tankeshwar 476 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.