Date Published: March 13, 2019
Publisher: Public Library of Science
Author(s): Woong Sik Jang, Seung Yeon Kwak, Win Lai May, Dong June Yang, Jeonghun Nam, Chae Seung Lim, Han-Chung Wu.
Dengue is an increasing public health concern worldwide and requires efficient laboratory diagnostics. We evaluated three commercially available dengue rapid diagnostic tests—the Humasis Dengue Combo NS1 & IgG/IgM (Humasis, Korea), SD Bioline Dengue Duo NS1 Ag & IgG/IgM (SD Bioline, Korea), and CareUS Dengue Combo NS1 and IgM/IgG kits (WellsBio, Korea)—and compared them to reference immunoglobulin M (IgM) or immunoglobulin G (IgG) ELISAs and quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays. In total, 109 dengue-positive samples from children with acute symptomatic dengue and 63 dengue-negative samples from febrile and asymptomatic individuals were collected. For the nonstructural 1 protein (NS1) Ag test, the sensitivity and specificity were in the following order: CareUS (79.82 and 100%), Humasis (63.30 and 100%), and SD Bioline (48.62 and 100%). For IgM and IgG, CareUS had the highest sensitivities and specificities (89.91 and 100%; 82.57 and 100%, respectively), followed by SD Bioline (60.55 and 100%, 77.98 and 100%, respectively), and Humasis (51.38 and 98.21%, 72.48 and 95.24%, respectively). The IgM kits were more sensitive than the NS1 Ag or IgG kits; however, combining NS1 Ag and IgM reduced the number of missed cases. Therefore, the NS1 Ag plus IgM dengue kits increase the accuracy of the results. In our study, the CareUS Dengue Combo NS1 and IgM/IgG kit showed higher accuracy in performance with reference to qRT-PCR and ELISA results.
Dengue fever is caused by four serotypes of dengue virus (DENV)—DENV1, DENV2, DENV3, and DENV4—and is transmitted mainly by Aedes aegypti. Since the end of the 20th century, dengue infection has been found to be common in subtropical areas, and has also been reported in urban areas [1, 2]. Prior to 1970, severe forms of DENV infection, such as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), were restricted to only nine countries . However, the disease is now endemic in more than 100 countries, including countries in Africa, the Americas, the Mediterranean region of the Middle East, Southeast Asia, and the Western Pacific [3, 4]. In 2015, 2.35 million cases of dengue were reported in the Americas alone, of which 10,200 cases were diagnosed as severe dengue and led to 1,181 deaths . The World Health Organization (WHO) estimates 390 million people are infected with dengue fever annually , resulting in 500,000 hemorrhagic dengue fevers that leads to 25,000 deaths every year . In particular, it has been reported that dengue infection in Myanmar predominately occurs in children aged less than 15 (97% and 98% respectively) with a total of 89,832 cases and 393 hospital deaths occurring between 2011 and 2015 . Tragically, DHF is a leading cause of hospitalization and death of children in several Asian countries. Case-fatality rates, although normally 2.5%, can exceed 20%, but can be reduced to < 1% with rapid recognition and proper treatment. Therefore, the early management of patients with dengue infections is essential to prevent the occurrence of severe forms of the disease, and the ability to rapidly confirm an acute dengue infection could aid in providing the accurate treatment and management of patients as early as possible . A total of 220 samples were assessed in this study. For the dengue-positive cases, there were 109 samples from children with acute symptomatic dengue confirmed by RT-PCR, IgM, and IgM/IgG ELISA (Fig 1). The patient included an almost equal ratio of males (52.29%) and females (47.71%). The mean age of the patients was 7.5 years (range 1–14 years). Acute phase samples from patients with suspected dengue were collected after 3 to 7 days of fever. To distinguish between primary and secondary dengue virus infections, we used a cutoff IgM/IgG ratio of 1.2, which was consistent with the published cutoff ratio range [15, 16]. There were 22 primary (20.2%) and 87 secondary infections (79.8%) among the dengue-positive cases. The serotype distribution of the 102 RT-PCR-based positive samples were DENV1 (77; 75.5%), DENV2 (23; 22.5%), and DENV4 (2; 2%). According to WHO guidelines, dengue-positive samples were classified as dengue (19; 17.4%), warning signs (63; 57.7%), or severe dengue (27; 24.7%). The dengue-negative cases yielded 63 samples from children with febrile non-dengue infections. All these samples were negative for dengue based on qRT-PCR and an anti-dengue IgM and IgG ELISA (Fig 1). Dengue fever is caused by the dengue virus and is a tropical disease transmitted by mosquitoes [17, 18]. Secondary infections can lead to life-threatening dengue hemorrhagic fever or dengue shock syndrome. As stated by the WHO for the Southeast Asia and Western Pacific region, about 1.8 billion people are at risk of dengue, putting a significant economic and disease burden on these countries [19, 20]. Myanmar has seen an increase in dengue fever over the past decade, and is now classified as a high-risk dengue country in the Asia-Pacific region . At present, a rapid diagnostic test kit for dengue fever can be used, but is in limited supply and rarely used in Myanmar . In addition, information on circulating serotypes in Myanmar is limited because it requires PCR, which is only available in the National Health Laboratory under the Department of Public Health and the Department of Medical Research . It was recently reported that DENV1 predominated in the 2013 outbreak, whereas serotypes 1, 2, and 4 were those mainly found in circulation in Myanmar in the 2015 outbreak . In this study, we used DENV samples collected at the Yankin Children Hospital in Yangon in Myanmar from October 2015 to August 2016. DENV serotypes were identified in 102 DENV PCR-confirmed patients, where DENV1 (71.29%), DENV2 (21.29%), and DENV 4 serotypes (1.85%) were detected. DENV3 was not detected. In the 102 DENV PCR samples, DENV1 was found to be the most predominant. Our results are similar to the results reported in 2013, but not to results reported in 2015. The reason for this is probably because the results of the experiments reported by Oo et al. for 2015  were derived from a small sample of 36 patients. In fact, the distribution of dengue type over the entire 2013–2015 period was similar to our results. Source: http://doi.org/10.1371/journal.pone.0213451