Evaluation of commercially available anti-dengue virus immunoglobulin M tests

Overview

The arthropod-borne flavivirus dengue virus (DENV) is found mostly in tropical and subtropical regions. Four distinct serotypes (DENV 1-4) cocirculate in many of the dengue-endemic regions of the world. Approximately 2.5 billion people live in areas at risk for acquiring dengue. Of an estimated 50 million infections annually, around 500 000 cases (of which a high proportion are children) are hospitalized with dengue haemorrhagic fever (DHF), a more severe form of the disease.

DENV infection can produce a broad spectrum of symptoms that range from mild febrile illness to severe disease. Clinical features are often nonspecific and therefore require laboratory confirmation, especially for surveillance and outbreak investigations. Virus isolation provides the most convincing evidence of infection, but facilities for culture are not always available. Detection of virusspecific RNA, by nucleic acid amplification methods such as polymerase chain reaction (PCR), provides accurate diagnosis but requires expensive reagents and equipment, laboratory infrastructure, and well-trained staff. Stringent quality control is necessary to avoid false positive results due to contamination.

Serological assays that can detect virus-specific immunoglobulin M (IgM) or immunoglobulin G (IgG) antibodies to DENV are widely available and can provide an alternative to virus isolation or PCR to support the diagnosis of dengue fever. During infection, IgM antibodies can usually be detected approximately five days after onset of fever. However, serum specimens may be negative for these antibodies if collected too early. First-time (primary) DENV infections typically have a stronger and more specific IgM response; subsequent (secondary) infections show a weaker IgM response but a strong anti-DENV IgG response. These differing IgM response patterns to infection underscore the need to evaluate the sensitivity and specificity of commercially available tests, especially for diagnosis of secondary DENV infections. A WHO/TDR and PDVI Joint Workshop on Dengue Diagnostics and Dengue Classification/Case Management was held in Geneva in October 2004. Participants reviewed the range of diagnostic options for case management and control of dengue infection. An inventory of antigen and antibody detection tests for the diagnosis of dengue was developed by TDR. The group agreed that there is an urgent need to evaluate the performance of commercially available dengue diagnostic tests and established a PDVI-TDR working group to review priorities and develop ideal test specifications depending on whether tests are to be used for case management, epidemiological surveillance or vaccine efficacy trials. The dengue working group agreed that the highest priority is the evaluation of IgM detection tests in either a rapid test (RDT) or ELISA format.

TDR identified regional reference laboratories for Latin America and Asia. These would coordinate the activities of a network of dengue laboratories to evaluate the performance and utility of existing dengue diagnostics and related activities. This report describes the results of a laboratory-based evaluation of nine commercially available anti-DENV IgM tests, using a panel of well-characterized, archived serum specimens from persons with confirmed DENV infections and other potentially confounding infections and conditions.