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A new highly sensitive method may offer early diagnosis of dengue virus infection by detecting the viral components, such as RNA. The researchers from Gen-Probe Incorporated of San Diego and the Centers for Disease Control and Prevention (CDC) report their findings in the April 2009 issue of the Journal of Clinical Microbiology.
Dengue virus (DENV) is currently recognized as the most widely spread mosquito-borne virus. The World Health Organization reported between 50 million and 100 million cases of dengue-related disease in 2004. Mosquitoes' expansion of their geographical distribution throughout the tropical regions of South East Asia and the Americas over the last two decades is largely attributed to population growth as well as increased international travel and trade.
Early diagnosis of DENV has proved challenging largely due to the undifferentiated fever and other unspecific symptoms that patients present with five to seven days post-infection. Patients that present with acute dengue disease are viremic, but may not yet have developed detectable antibodies. Serological testing has been the main method used for diagnosing DENV, but this approach generally only confirms infection after the patient has recovered.
Reverse transcription (RT)-PCR testing has been used more frequently for diagnosing dengue virus, however sensitivity levels only range between 40 percent and 80 percent in serologically confirmed cases. Transcription-mediated amplification (TMA) is a highly sensitive blood screening method with detection limits of approximately 95 percent. In the study researchers compared the sensitivity of TMA to that of (RT)-PCR and found TMA to be 10 to 100 times more sensitive. Further testing showed that among samples from patients with serologically confirmed dengue infection, TMA detected DENV RNA in 80 percent of specimens that were negative according to the RT-PCR test used and in all specimens with positive RT-PCR results.
"Our results indicate that TMA detects DENV RNA in approximately 89 percent of acute-phase serum specimens and therefore may provide a useful diagnostic test for acute DENV infections," say the researchers.
Reference: J.L. Munoz-Jordan, C.S. Collins, E. Vergne, G.A. Santiago, L. Petersen, W. Sun, J.M. Linnen. 2009. Highly sensitive detection of dengue virus nucleic acid in samples from clinically ill patients. Journal of Clinical Microbiology, 47. 4: 927-931.