CAPTURE ELISA - Improvement in specificity and sensitivity for IgM detection
PROBLEM :
SOLUTION :
In India, there is a high prevalence of IgG antibodies in Infectious diseases. Thus if high affinity antibodies to the specific antigen is present in the sample then, it may preferentially bind to the antigen. This may interfere with the detection of antigen specific IgM antibodies. This may lead to false negative or even false low positive IgM results. Also Rheumatoid factor (RF) has very high prevalence in India which are antibodies directed to the Fc region of IgG, IgM and IgA type antibodies, are produced during Rheumatoid arthritis. Presence of IgG RF may also lead to a false positive IgM results.
In u CAPTURE ELISA, the microtitre plates are coated with anti IgM antibodies. This step helps in binding of only IgM antibodies in first step and removes all IgG in first step washing and eliminating any chances of IgG cross reactivity in IgM tests. During the second step specific antigen bound to the enzyme conjugate is added. This, then acts on the appropriate substrate to give a colored product which can estimated calorimetrically to estimate the antigen specific IgM type of antibodies in the serum sample. This step eliminates the interference caused due to IgG RF.
Avidity testing advantage with Diesse ToRC IgG Avidity kits.
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Confirmatory test for ToRC diagnosis
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Test can be performed with the same ToRC IgG kit, no need to purchase separate avidity kit
ToRC IgG Avidity Testing - An important tool for discriminating recent from past TORC infection.
Avidity is defined as the measure of the functional binding strength of antibodies to multiple antigenic determinants (epitopes) on natural antigens. The IgM antibodies are detected for 4-8 weeks and indicate an acute infection whereas a positive result for IgG and negative for IgM gives more an indication of previous exposure and immunization . But sometimes it become difficult to differentiate between recent infection and past infection.
Problems because of which IgM can come positive in serum are :
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Persistence of IgM antibodies for months and year after infection
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reinfection with increase of IgM antibody response
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a polygonal IgM stimulation
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A non-specific IgM result in the affected test system.
Principle of Diesse ToRC IgG Avidity Test
Interpretation :
Avidity index > 40 % Avidity high-------> Previous exposure (more than 12 weeks) or Reinfection
Avidity index 30 - 40 % Avidity borderline ---------> No information about time of infection
Avidity index <30 % Avidity low ---------> Recent infection ( less than 12 weeks)
As per CSR responsibility, you do not need additional kit for avidity testing. We can provide you the additional reagent required for avidity testing on the same IgG kit .
Please contact us for ToRC Avidity Range
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Toxoplasma IgG Avidity
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Rubella IgG Avidity
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Cytomegalovirus IgG Avidity
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