Jpn. J. Infect. Dis., 56, 205-209, 2003

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Original Article

Evaluation of RT-PCR as a Tool for Diagnosis of Secondary Dengue Virus Infection

Areerat Sa-ngasang*, Sasitorn Wibulwattanakij1, Sumalee Chanama, Anantchai O-rapinpatipat1, Atchareeya A-nuegoonpipat, Surapee Anantapreecha, Pathom Sawanpanyalert and Ichiro Kurane2

National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi 11000, 1Sawanpracharak Hospital, Nakhon Sawan 60000, Thailand and 2Department of Virology I, National Institute of Infectious Diseases, Tokyo 162-8640, Japan

(Received September 11, 2003. November 25, 2003)


*Corresponding author: Mailing address: National Institute of Health, Department of Medical Sciences, Ministry of Public Health, 88/7 Tivanond Rd., Amphur Maung Nonthaburi 11000, Thailand. Tel: +66 2951 0000 ext. 99220, Fax: +66 2591 5449, +66 2951 1498, E-mail: areerat@dmsc.moph.go.th


SUMMARY: Dengue fever and dengue hemorrhagic fever are serious illnesses in many tropical and subtropical countries. Laboratory tests are essential for the confirmation of dengue virus infection. In the present study, we examined the reliability of reverse transcriptase polymerase chain reaction (RT-PCR) in the laboratory diagnosis of dengue, especially in secondary dengue virus infections. We defined the day when fever subsided as fever day 0. In primary dengue virus infection, the dengue viral genome was detected in all of the 7 samples which were collected on fever day -1 or earlier, in 3 of 4 samples on fever day 0, and in 1 of 2 samples on fever day 1. None of the samples collected on fever day 2 or later were positive by RT-PCR. In secondary dengue virus infection, the dengue viral genome was detected in all of the 28 samples which were collected on fever day -2 or earlier, in 25 of 26 on fever day -1, in 29 of 34 on fever day 0, and in 5 of 10 on fever days 1-2. None of the samples collected on fever day 3 or later were positive. Virus isolation and direct titration were attempted using the plasma samples. When the data of secondary infection cases were analyzed based on fever day, dengue viruses were isolated from all of the 5 samples which were collected on fever day -2 or earlier, in 5 of 13 samples on fever day -1, and in 4 of 22 on fever day 0, but were not isolated from any of the 4 samples collected on fever days 1 - 2. Viruses were directly detected in 7 of 11 samples on fever day -2 or earlier, in 4 of 13 on fever day -1, and in 1 of 16 on fever day 0. These results indicate that RT-PCR is more sensitive than virus isolation and direct virus titration for determining secondary dengue virus infection. The results also suggest that RT-PCR is a useful diagnostic test for confirmation of dengue virus infection in secondary infection as well as in primary infection, especially when plasma samples are collected before the fever subsides.


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