Challenges in diagnosing Zika—experiences from a reference laboratory in a non-endemic setting
Diagnosing a patient with Zika infection is not always straightforward. Here, we aim to describe our data collected from December 2015 to December 2017 and discuss the implemented algorithm and diagnostic challenges we encountered. At the National Reference Center for Arboviruses at the Institute of Tropical Medicine, Antwerp, Belgium (ITM), a commercial Zika virus (ZIKV) enzyme-linked immunosorbent assay (ELISA) detecting immunoglobulin (Ig) M and IgG, a commercial ZIKV immunofluorescence assay (IFA) detecting IgM, and an in-house Zika virus neutralization test (VNT) were implemented. For molecular detection of ZIKV, an in-house and a commercial real-time RT-PCR were applied. An algorithm, adapted from the European Centre for Disease Control and Prevention (ECDC), was implemented. Between December 2015 and December 2017, we tested 6417 patients for ZIKV. Of those, according to ECDC criteria, 127 (2.0%) were classified as a confirmed Zika infection of which 39 by RT-PCR (0.6%), 15 (0.2%) as a probable Zika infection, 73 (1.1%) as undefined, and 65 (1.0%) as false positive reactions. Main challenges were the brief window for detection of IgM, cross-reactivity of antibodies with other flaviviruses and malaria, and low VNT titers in the acute phase. In RT-PCR negative samples, classification of ZIKV infection as recent or past proved difficult, when IgM was negative. The majority of patients could be classified according to ECDC criteria, though 1.1% of patients remained “undefined” and 1.0% were ELISA false positive reactions. Complementary IFA IgM was of added value to increase IgM detection rates. Improved serological assays and more longitudinal data on antibody kinetics are needed.
KeywordsZika Diagnosis Serology Challenges
We would like to thank Prof. Dr. Jonas Schmidt-Chanasit, from the Bernhard Nocht Institute for Tropical Medicine WHO Collaborating Centre for Arbovirus and Haemorrhagic Fever Reference and Research National Reference Centre for Tropical Infectious Diseases, Hamburg, for providing us with the MR766 ZIKV strain.
The National Reference Center of arboviruses (Institute of Tropical Medicine) is partially supported by the Belgian Ministry of Social Affairs through a fund within the Health Insurance System. The Institute of Tropical Medicine was partially funded by European Union’s Horizon 2020 research and innovation program under ZikaPLAN grant agreement no. 734584.
Compliance with ethical standards
The Institutional Review Board (IRB) of the ITM was notified on the publication of these data. As approved by the IRB, data from patients presenting at the ITM can be used for research purposes as long as the patient does not object and his/her identity is not disclosed to third parties. Some patient results were already published elsewhere (Steinhagen K (n = 4), Lustig (n = 7)).
Conflict of interest
The authors declare that they have no conflict of interest.
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