Fever in the returned traveller: the utility of the Platelia Dengue NS1 antigen enzyme immunoassay for the diagnosis of dengue in a non-endemic setting.

Investigating fever in the returned traveller can be difficult and costly. Dengue is one of the most frequently reported aetiologies. NS1 is a non-structural dengue virus protein detectable during acute infection. The aim of this report is to describe the utility of the Platelia Dengue NS1 antigen enzyme immunoassay (EIA) for detection of dengue in a non-endemic region compared to a composite gold standard of contemporaneous molecular testing and seroconversion. We performed a retrospective analysis of all dengue serology tests from 6 February 2012 to 5 December 2018. Dengue serology and in-house flavivirus molecular results were identified using the laboratory information management system. Dengue serology was performed using the Bio-Rad Platelia Dengue NS1 antigen EIA, and Abbott Panbio Dengue IgG and IgM EIA. True positive NS1 result was defined as positive molecular test within one week of the positive NS1 result or seroconversion within 120 days. NS1 negative samples that remained negative to all dengue markers on repeat more than 10 and up to 120 days after were labelled as true negatives. More than 75% of cases had a serology pattern consistent with primary dengue. Sensitivity and specificity of NS1 Ag EIA was 96.4% (95% CI 92.3-98.7%) and 98.4% (95% CI 94.5-99.8%), respectively. Performance was poorer in serotype 4 infections (sensitivity 50%). Platelia Dengue NS1 antigen EIA test performance in the returned traveller cohort fulfils the remit as a single diagnostic test for acute dengue infection.