Page 191 - TBE_Book_V2_2019

Chapter 10: Diagnosis

Table 2: Possible serologic constellations, their possible interpretation,
and steps necessary for confirmation of TBE infection

Serologic constellation Local CSF
IgM IgG IgM IgG antibody Interpretation Activity
(serum) (serum) (CSF) (CSF) production
Serologic control after
False-positive IgM; 7 days;
+ - - - - early phase of re-testing with other
infection
test format
Possible status after Serologic control after
previous 7 days (increase in
+ + - - - vaccination; very antibodies);
early in state of TBE cerebrospinal
infection re-testing after 7 days
Past infection or Avidity testing in cases
- + - - - vaccination; passive with neurologic
antibody transfer symptoms
Acute or post-acute
+ + + + +
TBE infection
Not Possibly incorrect Re-testing with other
- - - +
calculable result test format
Not Possibly incorrect Re-testing with other
- - + -
calculable positive result test format

be like the HI test (the author’s personal After 2 flavivirus infections or vaccinations, a
observation). IF assays that detect IgM secondary response similar to the one seen in
antibodies against TBEV are moderately the HI test can often be detected as a high and
specific and occasionally show low levels of broadly cross-reactive titer (the author’s
cross-reactivity to other anti-flavivirus personal observation).
antibodies following a recent infection or
vaccination in the patient’s history (the Neutralization test
author’s personal observation). According to
our laboratory’s experience, IF assays that The neutralization test (NT) exploits the
detect IgG antibodies against TBEV perform capacity of antibodies to neutralize infectious
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specifically if there is only a TBEV infection or viruses, with several different formats
vaccination in the medical history. In contrast, available. One type of NT uses a standardized
diagnosis of patients with a history of infection virus preparation and varying serum dilutions,
or vaccination by a flavivirus other than TBEV while another format uses a standardized
can be difficult due to cross-reacting serum dilution and varying virus concentra-
antibodies. tions. Other examples are the plaque
reduction NT (PRNT), which is used to
Low antibody titers that subsequently become evaluate the neutralization titer by analyzing
undetectable occur following TBE vaccination the serum dilution at which the number of
and therefore IF assays are not recommended viral plaque-forming units is reduced by 50%
to test for immunity against TBE. or 90%, and the ‘tissue culture infection dose

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