Commercial Molecular Assay Validated for Dengue Virus Outbreak

Dengue virus (DENV) is a member of the viral genus Flavivirus (family Flaviviridae) that is transmitted by mosquitos, causing endemic and epidemic outbreaks in tropical and subtropical areas.

Accurate, rapid, and early diagnosis of DENV infections is important for public health and optimal clinical care; however, the gold standard method of cell culture-dependent isolation of DENV during the acute phase of infection is time-consuming and cumbersome.

Medical scientists at the National Cheng Kung University (Tainan, Taiwan) collected serum samples from patients with suspected DENV infection between July and November 2015. Sera from patients with suspected DENV infection were screened using the one-step immunochromatographic SD BIOLINE Dengue DuoDengue NS1 Ag + Ab Combo assay. This rapid assay contains two test devices, which can simultaneously detect the levels of nonstructural protein 1(NS1) antigen, and immunoglobulin M (IgM) and IgG in a sample, respectively, within 15 minutes.

Viral ribonucleic acid (RNA) was extracted from serum samples and an extraction control sample using a QAIamp viral RNA mini kit or the automated extraction system LabTurbo Virus mini Kit in LabTurbo 48 Compact System. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis of viral loads was performed using LightMix dengue virus EC kit, which is capable of identifying all four dengue serotypes.

A total of 8,989, 8,954, and 1,581 samples were subjected to NS1 antigen detection, IgM and IgG detection, and LightMix assays, respectively. The LightMix assay yielded a linear curve for viral loads (VL) between 102 and 106 copies/reaction, and the minimum detection limits for DENV serotype 1 (DENV1) and DENV2, DENV3, and DENV4 were 1, 10, and 100 focus forming units (FFU)/mL, respectively. There was 88.9% concordance between the results obtained using the NS1 antigen combo kit and by LightMix analysis, and the diagnostic sensitivity and specificity of the two methods were 89.4% and 100%, and 84.7% and 100%, respectively.

The authors concluded that the LightMix assay was effective for early diagnosis of DENV infection. The data indicated that high viral loads during primary infection in elderly patients may be a positive predictor for severe illness, and may contribute to high mortality rates. The study was published on October 12, 2016, in the journal Public Library of Science Neglected Tropical Diseases.

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National Cheng Kung University