This would be my second posting about my SIP. Today I will be talking about how do you detect presence of Dengue antibodies in patient’s serum.
Firstly I will discuss about the introduction of Dengue virus. Dengue is a flavivirus, it is found in large areas of the tropics and subtropics. Transmission is by mosquito, principally Aedes aesgypti and Aedes albopictus. Dengue virus infection causes a spectrum of clinical manifestations ranging from symptomatic to fatal hemorrhagic disease. Classic dengue is characterized by sudden onset of fever, intense headache, myalgia, arthralgia and rash. A dysphasic febrile course is common, as it is insomnia and anorexia with bitter or loss of taste. Dengue hemorrhagic fever and dengue shock syndrome are severe complications often associated with secondary dengue infection.
In endemic regions, patients diagnosed with dengue fever generally have secondary infection. Consequently, detection of antibodies to dengue is valuable procedure, particularly in second and subsequent infections where the occurrence of complications is high. Traditionally, haemagglutination-inhibition (HAI) titers have been used to classify infections as primary or secondary. The current definition depends on an assay of paired serum specimens separated in time by at least 7 days, although any acute specimen with an HAI titer ≥ 1:1280 is defined as coming from a patient with seconday flavirus infections.
My company uses this instrument called Panbio Dengue Duo Cassette. It is for the qualitative presumptive detection of IgM and IgG antibodies to dengue virus in human serum. The assay can be used for the presumptive differentiation between primary and secondary infection. This test should only be used for patients with signs and symptoms that are consistent with dengue virus infection. Positive results are presumptive and must be confirmed by virus isolation, paired serum analysis, antigen detection by immunohistochemistry or viral nucleic acid detection for conifrmation of dengue virus infection.
The sensitivity of this assay has been set so that in patients with primary dengue, IgM is positive while IgG is negative. In contrast, patients with secondary infections will have a postitive IgG result with or without postive IgM result.
The principle of this assay, is when present in the patient sample, dengue-specific IgM or IgG antibodies bind to anti-human IgM or IgG antibodies immobilizied in 2 lines across the cassette membrane. Colloidal gold complexes containing recombinant dengue 1-4 antigens are captured by the bound patients IgM or IgG to give visible pink line(s). a procedural control is included to indicate that the assay has been performed correcty.
By Ivan Ng
4 August 2008 (Mon)