Variable Sensitivity in Molecular Detection of Zika Virus in European Expert Laboratories: External Quality Assessment, November 2016

Zika virus (ZIKV) infections are a significant public health concern. A strong capability for ZIKV detection is an absolute requirement for adequate preparedness and response strategies and individual patient care. The objective of this study was to assess and improve the capability of European expert laboratories for molecular testing for ZIKV through an external quality assessment (EQA) scheme. Laboratories were provided a panel of 12 samples which included negative samples, samples containing African-or Asian-lineage ZIKV at various concentrations (10(3) to 10(9) copies/ml), and samples containing dengue virus, yellow fever virus, or chikungunya virus. The results were analyzed on the basis of the outcomes of testing for the samples and the extraction and detection method used. Samples with a ZIKV RNA status scored correctly by >50% of the laboratories were designated the core sample. A total of 85 panel outcomes were submitted by 50 laboratories in 31 countries. The results designated all samples as core samples. Thirty-three percent (28/85) of the panel outcomes identified all samples. Analysis at the laboratory level showed that only 40% of the laboratories (20/50), representing 45% of the countries, scored sufficiently; i.e., they had at least one test operational that scored all core samples correctly. There is a need for improvement of the molecular detection of ZIKV in 60% of the participating laboratories. While the specificity of the tests was more robust, the results of the EQA showed large variation in test sensitivity. Improvements should focus on both nucleic acid extraction and ZIKV detection methods.