Background
- The idea is to detect antigen or antibodies.
- The most common used technique is ELISA (enzyme linked imunosorbent assay), for example:
- detecting IgG of CMV infection (IgG pass through the placenta of the mother)
- Wells coated with antigen --> serum --> conjugate (with enzyme) --> substrate
- When specific binding occurs, the substrate will be broken and release colour change.
- Another possibilities:
- CLIA (chemoluminescense assay)
- using foton measurement instead of optical density in ELISA, in our lab for example for EBV
- Conventional technique
- for example: detecting treponemal antigen using RPR/ VDRL (non specific but very sensitive) or TPPA (specific)).
- RPR is more specfic than VDRL but VDRL can be automatized.
- the earlier the syphillis, the larger the chance that RPR can be back to 0. RPR gives good indication on treatment, for example two titer dilution. TPPA does not give a good indication in treatment effect.
- do also HIV test in newly diagnosed syphilis. If it is negative, repeat the test within 3 months.
- galactomanan
- in hematooncology departement, weekly screening can be performed. An increasing trend can be treated.
- cut off: 0.5, higher in bronchoalveolar lavage than in blood.
CMV
- detecting IgM of CMV infection
- wells coated with antibodies anti IgM--> serum --> specific antigen IgM with conjugate --> substrate.
- antibodies on wells instead of antigen because IgM is made in recent infection (high number) and bigger molecules, and this should be sorted out first (?)
- viral load CMV in blood using PCR does not say much because the shedding of the virus is not constant.
- If CMV is found in amniotic fluid, it means that the fetus is infected with CMV. 40% risk of sequelae if the infection occurs in the first trimester.
EBV
- Remember for a possible cross reaction: positive IgM EBV can be caused by IgM CMV. For the confirmation EBNA IgG can be performed. This EBNA IgG is formed normally 3 months after acute infection.
- Mononucleosis
- To differentiate new from old, perform EBNA IgG (it became positive after IgM), positive result exclude the possibility of recnet infection.
Toxoplasmosis
- IgM toxoplasmosis fluorescense decrease more rapdi than IgM ELISA
- The idea is to detect antigen or antibodies.
- The most common used technique is ELISA (enzyme linked imunosorbent assay), for example:
- detecting IgG of CMV infection (IgG pass through the placenta of the mother)
- Wells coated with antigen --> serum --> conjugate (with enzyme) --> substrate
- When specific binding occurs, the substrate will be broken and release colour change.
- Another possibilities:
- CLIA (chemoluminescense assay)
- using foton measurement instead of optical density in ELISA, in our lab for example for EBV
- Conventional technique
- for example: detecting treponemal antigen using RPR/ VDRL (non specific but very sensitive) or TPPA (specific)).
- RPR is more specfic than VDRL but VDRL can be automatized.
- the earlier the syphillis, the larger the chance that RPR can be back to 0. RPR gives good indication on treatment, for example two titer dilution. TPPA does not give a good indication in treatment effect.
- do also HIV test in newly diagnosed syphilis. If it is negative, repeat the test within 3 months.
- galactomanan
- in hematooncology departement, weekly screening can be performed. An increasing trend can be treated.
- cut off: 0.5, higher in bronchoalveolar lavage than in blood.
CMV
- detecting IgM of CMV infection
- wells coated with antibodies anti IgM--> serum --> specific antigen IgM with conjugate --> substrate.
- antibodies on wells instead of antigen because IgM is made in recent infection (high number) and bigger molecules, and this should be sorted out first (?)
- viral load CMV in blood using PCR does not say much because the shedding of the virus is not constant.
- If CMV is found in amniotic fluid, it means that the fetus is infected with CMV. 40% risk of sequelae if the infection occurs in the first trimester.
EBV
- Remember for a possible cross reaction: positive IgM EBV can be caused by IgM CMV. For the confirmation EBNA IgG can be performed. This EBNA IgG is formed normally 3 months after acute infection.
- Mononucleosis
- To differentiate new from old, perform EBNA IgG (it became positive after IgM), positive result exclude the possibility of recnet infection.
Toxoplasmosis
- IgM toxoplasmosis fluorescense decrease more rapdi than IgM ELISA
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