Commercial Molecular Assay Validated for Dengue Virus Outbreak

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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