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-po lymerase chain reaction (RT-PCR). Out of the 100 samples tested, none was p ositive by either the Chomczynski-Sacchi technique or TRIzol (R), and six w ere positive using the QIAamp (R) viral RNA kit. Of the six positive sample s, only one was collected before 5 days of the beginning of the disease, an d it was also positive for viral isolation. These results were confirmed la ter by serology (MAC-ELISA) that showed that 19 samples were positive for I gM antibodies against dengue. These data indicate that PCR is a useful meth od for detection of dengue virus infections in IgM-positive samples, and th e best method of RNA extraction from clinical samples, to be used for dengu e diagnosis by PCR is the QIAamp (R) Viral RNA kit. (C) 2001 Elsevier Scien ce B.V. All rights reserved.