Tick-borne Encephalitis in Childhood: Rare or Missed?

Magnus E. A. Hansson, MD; Claes Örvell, MD, PhD; Mona-Lisa Engman, MD, PhD; Katarina Wide, MD, PhD; Lars Lindquist, MD, PhD; Karl-Johan Lidefelt, MD, PhD; Mikael Sundin, MD, PhD


Pediatr Infect Dis J. 2011;30(4):355-357. 

In This Article

Patients and Methods

During 2003–2008, 3635 anti-TBE serologies were obtained at our hospital. These tests were requested by our own hospital, county hospitals, and general practitioners. Overall 998 patients (27%) were positive for anti-TBE immunoglobulin M (anti-TBE IgM) and/or G (anti-TBE IgG). These patients were asked retrospectively (May 2009) to fill in a questionnaire regarding symptoms prior to serology and to give consent to participate. Responses were obtained from 703 patients (70%), 32 (3.2%) were deceased and 13 (1.3%) could not be reached. Among respondents, 30 (4.3%) declined participation. Thus, 673 patients (67%), males/females 1/1.1, were available for further analysis. The study was approved by the Regional Ethics Review Board.

Serodiagnostic Testing for TBE

Serum anti-TBE IgM and G were determined (accredited test procedures) by enzyme immunoassays (Siemens Healthcare Diagnostics, Deerfield, IL) at the Virology Laboratory, Department of Microbiology in Huddinge, Karolinska University Laboratory. The serodiagnostic criterion was a positive anti-TBE IgM or increased titer (≥4-fold) of anti-TBE IgG between acute and convalescent samples.

Clinical Chemistry

Laboratory results (ie, blood count, inflammatory indices, and cerebrospinal fluid [CSF] analysis) other than anti-TBE IgM and G were collected from patient charts. Tests were performed at accredited laboratories, mainly the Karolinska University Laboratory. The reference intervals are congruent with <5% variation.


Proportions were compared using Fisher exact test or, when sample size allowed, the χ2-test. Individual samples were analyzed using the Mann-Whitney U test or the Kruskal-Wallis test followed by Dunn multiple comparison test when appropriate. Statistical significance was set at P < 0.05.


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