Performance of rapid tests in the management of dengue fever imported cases in Lazio, Italy 2014-2019.

Five years of laboratory records were reviewed to establish the performance of two dengue rapid assay (RDT) for acute dengue diagnosis in a non-endemic country: • The two rapid assays showed high specificity and sensitivity. • NS1 antigen was the most reliable marker of dengue acute infection. • IgM positivity in the absence of NS1 and IgG often results from non-specific reactivity of the RDTs. • The sole detection of IgG was never indicative of acute dengue infection. • No secondary infections were observed in the studied population. • The combined use of NS1 and IgM/IgG detecting RDTs increases diagnostic sensitivity. In Italy, dengue virus is the most frequent agent of imported viral infections. The use of rapid diagnostic tests (RDTs) may be of help as a preliminary user-friendly quick assay to facilitate dengue diagnosis, as ordinary laboratory diagnosis of dengue fever may require special efforts in terms of tools availability, interpretation of results, and skilled personnel. The performance of RDTs, however, may vary according to different epidemiological and laboratory background. We reviewed five years of laboratory records of two dengue RDT results (Colorimetric SD-Bioline Dengue-Duo-RDT and Fluorimetric SD-Biosensor-STANDARD-F-Dengue-RDT), able to detect viral NS1 antigen and specific IgM and IgG. Diagnostic parameters were calculated using as reference the results of molecular (RT-PCR) and serological (immunofluorescence, IFA) tests. Overall performance, calculated considering the final case definition, was included in the accuracy assessment of RDTs. The combined use of NS1 and IgM/IgG RDT for the detection of acute dengue cases resulted in an overall sensitivity and specificity of 87.2% and 97.9% for Colorimetric RDT, 96.2% and 96.2% for Fluorimetric RDT. NS1 was the most reliable marker of acute infection, while IgM resulted falsely positive in nine samples, including sera derived from 2 Zika and 4 non-arbovirus infected patients. The inclusion of RDT in the diagnostic algorithm is of undeniable help in the prompt management and surveillance of dengue infection in non-endemic areas. Confirmatory tests are, however, necessary to rule in or rule out dengue fever diagnosis. [ABSTRACT FROM AUTHOR]