Single-tube nested PCR using immobilized internal primers for the identification of dengue virus serotypes.

Molecular techniques based on the detection of genomic sequences by reverse transcription (RT)-PCR, nested PCR, or real-time PCR have made possible the rapid diagnosis of dengue virus (DENV) infections, and these approaches have been accepted by clinical laboratories as the new standard method for the detection of dengue virus in acute-phase serum samples. One of these PCR-based assays, the two-step RT nested PCR (RT-NPCR) technique is used routinely in laboratories worldwide. In the present study, the two-step RT-NPCR as described by Lanciotti et al. [Lanciotti, R.S., Calisher, C.H., Gubler, D.J., Chang, G.J., Vorndam, A.V., 1992. Rapid detection and typing of dengue viruses from clinical samples by using reverse transcriptase-polymerase chain reaction. J. Clin. Microbiol. 30, 545-551] was adapted to a novel single-tube nested PCR (STNPCR) format, which is less prone to cross-contamination and reduces reaction cost and time. When standards for each dengue serotype were tested, the detection limit of the STNPCR was at least 10 copies for DENV-1 and 100 copies for DENV-2 and DENV-3, whereas the detection limit for the two-step RT-NPCR was 100 copies for each serotype. Sera from 22 patients with confirmed DENV-3 infections and from 14 healthy individuals were then tested in the STNPCR format using the system described by Lanciotti et al. as the reference standard. The results indicated a sensitivity of 75.9% (CI 95%, 60.3-91.4) and a specificity of 100% for the RT-STNPCR. Although RT-STNPCR was less sensitive than the conventional two-step RT-NPCR for the detection of virus in serum samples, it was still adequately sensitive, and the advantages associated with a single-tube format may outweigh the somewhat lower assay sensitivity, making it useful for diagnosis in the field.