Dengue is a common acute viral febrile illness in the tropics. Dengue fever (DF), caused by a mosquito-borne virus of the flaviviridae family, is endemic to India and can present with a wide range of clinical manifestations. It comprises four distinct serotypes (DEN-1, DEN-2, DEN-3 and DEN-4). Typical DF is characterized by high fever, severe headache, myalgia, arthralgia, retro-orbital pain and maculopapular rash. Some patients develop petechiae, bruising or thrombocytopenia. The National Vector Born Disease Control Programme (NVBDCP) in India reported 111,880 dengue cases and 227 deaths due to dengue in year 2016. The overall case fatality rate (CFR) of dengue fever is less than 1%. However CFR of patients who progress to develop dengue haemorragic fever is between 3–5%. Although resulting in an estimated 372 (210–520) DALYs per million inhabitants in Southeast Asia , approximately 90% of patients with dengue infection remain asymptomatic. It is, however, likely that many of the patients who do present with mild-moderate symptoms of dengue are inappropriately prescribed antibiotics.

Recognition of acute dengue infection may be challenging since the symptoms are non-specific and resemble several other causes of acute undifferentiated febrile illness, particularly in areas where there are other vector-borne diseases. The World Health Organization (WHO) syndromic case definition for dengue can help in identifying dengue cases in endemic areas. However, the syndromic approach alone may be inadequate in the diagnosis or management of severe dengue cases.  The clinical presentation of acute dengue infection is non-specific, but a proportion of patients progress to severe dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS). Therefore, early and accurate diagnosis of dengue infection and initiation of appropriate treatment are the key components in the management of severe dengue infection.

The characteristics of an ideal dengue diagnostic test depend on the purpose for which the test will be used. The ideal test for early diagnosis of dengue infection should be able to distinguish it from other diseases of similar clinical spectrum (such as malaria, leptospirosis, typhoid, typhus and chikungunya). The test needs to be highly sensitive during the acute stage of infection, rapid, inexpensive, easily performable and can be utilised at temperatures above 30 °C.

The target product profile (TPP) of an ideal test for use for the epidemiological surveillance and outbreak investigation of dengue should include giving positive results as soon as possible after onset of symptoms to provide early warning. Unlike the TPP needed for routine use in disease control programmes, these types of test needs to be highly specific and should be able to determine the dengue virus serotypes. The second priorities of an ideal test for epidemiological surveillance and outbreak investigations should be its ability to distinguish between primary and secondary infection, its high throughput capacity and long shelf life.

Current WHO recommendations for the diagnosis of dengue include enzyme-linked immunosorbent assay (ELISA)-based detection of dengue-specific Immunoglobulin M (IgM) antibodies or a ≥4-fold increase in the titre of total antibodies to dengue virus in paired acute and convalescent sera, or detection of dengue virus by reverse transcription–polymerase chain reaction (RT-PCR). In the Indian context, the government of India’s National Vector Borne Disease Control Programme (NVBDCP) guidelines from 2015 recommend the use of an ELISA-based antigen detection test (NS1) for diagnosing the cases from day 1 to day 5 of illness, and the antibody detection test IgM Capture ELISA (MAC ELISA) for diagnosing the cases after the 5th day of onset of disease for confirmation of dengue infection.

However, these tests are expensive, time-consuming, arduous, technologically demanding and are not always available in most resource-limited settings and during epidemics. Hence, a large fraction of medical practitioners depend on readily available rapid diagnostic test (RDT) kits which are cheaper and have less turn-around time for the early diagnosis of dengue infection. Most of the commercially available RDTs are based on immuno-chromatographic or ELISA methods to detect IgM and Immunoglobulin G (IgG) antibodies- with or without NS1 antigen- in the serum of the patients. Many different RDT kits are manufactured in India (and used internationally) and other RDTs that are not produced in India but are registered in the country are available commercially. The latter are widely used for the diagnosis of dengue fever in secondary and tertiary care centres across India as these give results within an hour and are technically less demanding.

The issue, however, lies with the reliability and performance of these tests, which are yet to be independently evaluated against an acceptable reference standard in India.  A WHO/TDR/PDVI laboratory network in 2009 evaluated selected commercial ELISAs and first-generation rapid diagnostic tests, finding that ELISAs generally performed better than rapid tests. They, however, did not look at NS1 antigen based rapid tests or combination tests, and none of the study sites were within India. There is limited evidence of evaluation of such RDTs against clinician based diagnosis. However, comparison with a laboratory-confirmed diagnosis based on ELISA is needed to ensure the robustness of the results. Therefore, in this study, we propose to  evaluate readily available commercial rapid diagnostic test kits for the diagnosis of dengue fever.

In this laboratory-based phase 2 diagnostic evaluation study using archived serum samples, we will evaluate the sensitivity and  specificity of six commonly used rapid diagnostic test kits in India manufactured by five different manufacturers:  Panbio Diagnostics,  Australia; Standard Diagnostics, Korea;  J. Mitra, India;  Zephry Biomedicals, India; and MP diagnostics,USA.