Instructor, Medicine - Infectious Diseases
A number of diagnostic tests are available for dengue virus (DENV) detection, including a variety of nucleic-acid amplification tests (NAATs). However, reports describing the direct comparison of different NAATs are limited. In this study, we report the design of an internally-controlled, real-time reverse-transcriptase PCR (rRT-PCR) that detects all four DENV serotypes but does not distinguish between them (the pan-DENV assay). Two-hundred clinical samples were then tested using four different DENV RT-PCR assays: the pan-DENV assay; a commercially-produced, internally-controlled DENV rRT-PCR (the Altona assay); a widely-used hemi-nested RT-PCR; and a serotype-specific, multiplex rRT-PCR assay. The pan-DENV assay had a linear range extending from 7.0 to 1.0 log10 complimentary DNA (cDNA) equivalents/μL and a lower limit of 95% detection ranging from 1.7 to 7.6 cDNA equivalents/μL depending on the serotype. When measured against a composite reference standard, the pan-DENV assay proved more clinically sensitive than either the Altona or hemi-nested assays, with a sensitivity of 98.0% compared to 72.3% and 78.8%, respectively (p≤0.0001 for both comparisons). The pan-DENV assay detected DENV in significantly more samples collected on or after day five of illness and in a subgroup of patients with detectable anti-DENV IgM at presentation. No significant difference in sensitivity was observed between the pan-DENV assay and the multiplex rRT-PCR, despite the presence of an internal control in the former. The detection of DENV RNA late in the course of clinical illness should serve to lengthen the period during which a confirmed, molecular diagnosis of DENV infection can be provided.
View details for DOI 10.1128/JCM.00548-13
View details for Web of Science ID 000320595800024
View details for PubMedID 23637298
Dengue fever results from infection with one or more of four different serotypes of dengue virus (DENV). Despite the widespread nature of this infection, available molecular diagnostics have significant limitations. The aim of this study was to develop a multiplex, real-time, reverse transcriptase-PCR (rRT-PCR) for the detection, quantitation, and serotyping of dengue viruses in a single reaction.An rRT-PCR assay targeting the 5' untranslated region and capsid gene of the DENV genome was designed using molecular beacons to provide serotype specificity. Using reference DENV strains, the assay was linear from 7.0 to 1.0 log₁₀ cDNA equivalents/µL for each serotype. The lower limit of detection using genomic RNA was 0.3, 13.8, 0.8, and 12.4 cDNA equivalents/µL for serotypes 1-4, respectively, which was 6- to 275-fold more analytically sensitive than a widely used hemi-nested RT-PCR. Using samples from Nicaragua collected within the first five days of illness, the multiplex rRT-PCR was positive in 100% (69/69) of specimens that were positive by the hemi-nested assay, with full serotype agreement. Furthermore, the multiplex rRT-PCR detected DENV RNA in 97.2% (35/36) of specimens from Sri Lanka positive for anti-DENV IgM antibodies compared to just 44.4% (16/36) by the hemi-nested RT-PCR. No amplification was observed in 80 clinical samples sent for routine quantitative hepatitis C virus testing or when genomic RNA from other flaviviruses was tested.This single-reaction, quantitative, multiplex rRT-PCR for DENV serotyping demonstrates superior analytical and clinical performance, as well as simpler workflow compared to the hemi-nested RT-PCR reference. In particular, this multiplex rRT-PCR detects viral RNA and provides serotype information in specimens collected more than five days after fever onset and from patients who had already developed anti-DENV IgM antibodies. The implementation of this assay in dengue-endemic areas has the potential to improve both dengue diagnosis and epidemiologic surveillance.
View details for DOI 10.1371/journal.pntd.0002116
View details for PubMedID 23638191