Dengue Rapid Diagnostic Tests Recycled For Serotyping

Dengue Rapid Diagnostic Tests (RDT), in which a drop of blood is loaded onto a paper strip in a plastic cassette, are simple to use and have good diagnostic accuracy. However, four types of dengue virus circulate in most tropical areas and their patterns of circulation are of epidemiological importance since they play a role in the severity and propagation of the disease.

An international team of tropical medicine specialists led by those at Mahidol University (Salaya, Thailand) collected blood samples from 99 consenting patients admitted with symptoms meeting the international criteria for dengue infection from August to November 2013. At another hospital 362 consenting patients with undifferentiated fever who tested negative by malaria RDT were enrolled from July to October 2012, and both venous whole blood and capillary whole blood from finger pricks were collected.

The samples were assayed with the SD Bioline Dengue Duo RDT (Standard Diagnostics, Kyonggi-do, Korea) which is an in vitro immunochromatographic assay for the detection of dengue virus NS1 Ag and anti-dengue IgM/IgG antibodies in human serum, plasma, or whole blood, from finger-prick or venous blood. This test comprises a pair of test devices, a dengue NS1 Ag test on the left side, and a dengue IgM/IgG antibody (Ab) test on the right side. Dengue RNA was purified from the sample pad of the NS1 RDT loaded with virus isolates of the four serotypes, then quantified by real time reverse transcriptase polymerase chain reaction (RT-PCR).

All dengue positive neat, RDT and filter paper (FP) samples were tested by real-time RT-PCR for serotyping. All four DENV serotypes were found, with the majority of patients having DENV-3 (81%; 42/52) followed by DENV-2 (10%; 5/52), DENV-4 (4%; 2/52), and DENV-1(4%; 2/52) with one sample that could not be typed. There was 100% concordance between RDT and serum RT-PCR of infecting dengue serotype. The dengue serotypes at in the rural area at Salavan were mostly DENV-1 (80%; 113/142) followed by DENV-2 (12%; 17/142) and DENV-3 (4%; 6/142).

The authors concluded that their technique may also permit dengue envelope sequencing for deeper molecular epidemiology analysis from RNA purified from RDTs. This could greatly increase availability of dengue epidemiological data from previously inaccessible tropical areas by facilitating dengue confirmation tests and strain identification to aid surveillance and public health interventions. The study was published on May 9, 2016, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
Mahidol University
Standard Diagnostics