Abstract
BackgroundThe diagnosis of an acute or convalescent West Nile (WN) virus infection can be confirmed by various serological assays such as enzyme immunoassay (EIA), immunofluorescence assay (IFA), or neutralisation test (NT) which are conducted by a growing number of laboratories. However, as the degree of proficiency may vary between laboratories, quality control measures for laboratory diagnostics are essential.MethodsWe have performed an external quality assurance (EQA) programme for the serological detection of WN virus infection to assess the diagnostic quality of laboratories. The participating laboratories received a proficiency panel of 10 coded lyophilised test samples comprising four antisera positive for WN antibodies as positive controls, three antisera positive for antibodies against other heterologous flaviviruses plus one multireactive unspecific serum as specificity controls, and two negative serum samples.ResultsTwenty-seven laboratories from 20 different countries in Europe, the Middle East, the Americas and Africa participated in this EQA programme. Applying the proficiency criteria of this study, only eight laboratories correctly analysed all samples with their respective EIA, IFA or NT methods. Eighteen laboratories correctly identified between 77.8 and 90% of the samples, and one laboratory identified only 70% correctly with a clear need to eliminate cross-reactivity with other antisera, particularly those elicited by yellow fever virus. Differentiation between the results for IgM and IgG was considered separately and revealed that IgM-antibodies were detected less frequently than IgG-antibodies (p < 0.001). However, the assay used was not a significant technical factor influencing laboratory performance.ConclusionThe EQA programme provides information on the quality of different serological assays used by the participating laboratories and indicates that most need to improve their assays, in particular to avoid cross-reactions with antibodies to heterologous flaviviruses.
Highlights
The diagnosis of an acute or convalescent West Nile (WN) virus infection can be confirmed by various serological assays such as enzyme immunoassay (EIA), immunofluorescence assay (IFA), or neutralisation test (NT) which are conducted by a growing number of laboratories
The aim of this study was to assess the diagnostic accuracy across participating laboratories and the tests they use by performing the first international external quality assurance (EQA) study for the serological detection of WN virus infection
While we found no significant variation when comparing the two different technical factors, i.e. assay type/format (EIA vs. IFA vs. NT) and assay origin, multivariate logistic regression analysis revealed that the samples used had a significant influence on laboratory performance (Table 3)
Summary
The diagnosis of an acute or convalescent West Nile (WN) virus infection can be confirmed by various serological assays such as enzyme immunoassay (EIA), immunofluorescence assay (IFA), or neutralisation test (NT) which are conducted by a growing number of laboratories. West Nile (WN) virus is a mosquito-transmitted flavivirus which belongs to the Japanese encephalitis virus group. It occurs throughout Africa, the Middle East, southern Europe, Russia, India and Indonesia, and was recently introduced into North America [1,2,3]. The availability of reliable serological assays such as the enzyme immunoassay (EIA), immunofluorescence assay (IFA) or neutralisation test (NT) is an important prerequisite for the clinical diagnosis and epidemiological surveillance of WN virus infections
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