leakage with or without haemorrhage. Intravenous rehydration is the therapy of choice, as it can reduce the fatality rate of severe cases to < 1%. Progression from non-severe to severe disease is difficult to define; however, appropriate treatment can prevent more severe clinical conditions. Does this test meet a medical need? Efficient, accurate diagnosis of dengue is of primary importance for clinical care (for early detection of severe cases, case confirmation and differential diagnosis from other infectious diseases), surveillance, outbreak control, pathogenesis, academic research, vaccine development and clinical trials. In relation to the EDL, antibody and antigen tests are essential for case management and surveillance. During the early stages of the disease, detection of antigens can be used to diagnose an infection, while, at the end of the acute phase of infection, serology is the method of choice. The choice of the assay for diagnosis depends on the time of sample collection and the purpose of testing (1). As for other Aedes-borne arboviruses, viraemia is present during the acute phase, and 90% of cases of primary and secondary dengue fever can be identified accurately from a single serum specimen collected during the first 10 days of illness, with DENV-1-4 real-time RT-PCR plus IgM ELISA or NS1 antigen ELISA (2, 3). Purposes of testing: In surveillance, the test is used to alert health authorities to possible emergence of an outbreak. Tests to identify the cause of an outbreak must be highly sensitive and specific in detecting DENV directly by isolation of the virus, its nucleic acid or its antigen in the acute phase of infection. Infection can also be diagnosed retrospectively from seroconversion of IgM or a four-times increase in IgG between the acute and convalescent values in serum samples collected > 14 days apart. A combination of IgM and either NAATs or antigen detection tests extends the window of detection of acute infection. The tests can also be used to assess the extent of an outbreak, inform control strategies and identify hotspots. High-throughput, ideally highly specific tests that can be used in various populations are required. In research, they are used to assess the impact of control interventions and improve understanding of the pathogen and its pathogenesis. DENV NS1 testing by ELISA or RDT is essential to confirm DENV infection directly, during onset of the disease. Both tests are straightforward EIA and RDT assays, and no significant difficulties have been reported by users. Disposal of the kits is routine and does not require special precautions. How the test is used: Depending on the set-up, the assay can be used at three levels of health systems: primary care centres, district centres and reference centres. A single test is sufficient if the sample is taken within the predefined time. As dengue fever is easily confused with non-dengue illnesses, particularly in non-epidemic situations, the DENV IVD can also be used as a differential test. The NS1 glycoprotein is produced by all flaviviruses and is secreted from mammalian cells. NS1 produces a very strong humoral response. Many studies have shown that detection of NS1 can be used to make an early diagnosis of DENV infection. Commercial kits for the detection of NS1 antigen are available, although they do not differentiate between DENV serotypes.

Prevalence: Dengue fever is the most rapidly spreading mosquito-borne viral disease in the world. Its incidence has increased 30 times over the past 50 years, with increasing geographical spread to new countries and, in the current decade, from urban to rural settings. An estimated 50 million cases of DENV infection occur annually, and approximately 2.5 billion people live in dengue- endemic countries. World Health Assembly resolution WHA55.17 in 2002 urged greater commitment to dengue by WHO and its Member States. Of particular significance is World Health Assembly resolution WHA58.3 on revision of the IHR in 2005, which included dengue fever as an example of a disease that may constitute a PHEIC, with implications for health security due to disruption and rapid epidemic spread beyond national borders. Socioeconomic impact: The global cost of dengue fever is estimated to be almost US$ 9 billion per year for prevention and control (4), and WHO estimated that more than 3 billion DALYs are lost annually from dengue illness.

Guidelines for patient care in the Region of the Americas (5).

In a review of the performance of commercially available NS1 RDTs, Blacksell et al. (6) summarized the results of evaluations of each of the SD Bioline Dengue Duo (Alere, USA) (four studies), the Panbio® Early Rapid NS1 (Alere, USA) (three studies) and the Dengue NS1 Strip (Bio-Rad, France) (12 studies) in various countries. The sensitivity of the RDTs varied from 48.5% to 98.9%, but their specificity was reasonably consistent, all being > 92%. Blacksell et al. (6), however, noted that the comparator used in the studies, RT-PCR or NS1-ELISA, was “skewed”, and the authors did not investigate the possibility of false-negative results by testing paired sera to determine a dynamic rise in serological assays such as IgM- or IgG-capture ELISAs. In studies of the diagnostic accuracy of NS1 assays in primary and secondary infections, the RDTs were generally more sensitive in primary than in secondary infections (7–10).

If only a subset of patients is tested during outbreaks or endemic periods for confirmation, the impact on overall budgets will be small.

Consent is required to obtain a serum sample. Dengue predominantly affects populations living in poverty, and access to high-quality diagnostics can reduce the burden and improve equity.