Comparison of techniques for extracting viral RNA from isolation-negative serum for dengue diagnosis by the polymerase chain reaction

Aiming at the improvement of the molecular diagnosis of dengue, three well-established methods of RNA extraction from serum of patients with clinical symptoms of dengue were compared. The methods were based on the QIAamp (R) Viral RNA kit, the Chomczynski-Sacchi technique and TRIzol (R). One hundred samples were examined using the same protocol for reverse transcription-polymerase chain reaction (RT-PCR). Out of the 100 samples tested, none was positive by either the Chomczynski-Sacchi technique or TRIzol (R), and six were positive using the QIAamp (R) viral RNA kit. Of the six positive samples, only one was collected before 5 days of the beginning of the disease, and it was also positive for viral isolation. These results were confirmed later by serology (MAC-ELISA) that showed that 19 samples were positive for IgM antibodies against dengue. These data indicate that PCR is a useful method for detection of dengue virus infections in IgM-positive samples, and the best method of RNA extraction from clinical samples, to be used for dengue diagnosis by PCR is the QIAamp (R) Viral RNA kit. (C) 2001 Elsevier Science B.V. All rights reserved.