The diagnostic gap

The diagnostic gap

Reliable diagnostics are the key to the prevention and management of NiV disease. Current diagnostics for NiV include laboratory-based serological testing and nucleic acid amplification techniques.

PCR is recommended as the most sensitive method for the diagnosis of an active NiV infection. Real-time PCR, which is almost exclusively used now, has been shown to be 1,000 times more sensitive compared to conventional PCR.

Next-generation sequencing and deep sequencing help a direct read of the viral genome, allowing virus and clade identification without prior knowledge of the composition. These methods, however, are expensive and not practical for screening larger numbers of samples.

NiV-specific IgM ELISA is an alternative serological approach where PCR is not available. Serological tests can directly detect NiV antigens, as well as IgM and IgG antibodies raised against NiV antigens. IgM ELISA is a first line NiV serological diagnostic test, followed by serum neutralisation or PCR as a confirmatory test. But they are less sensitive to minor genetic variation and more broadly cross-reactive within subtypes and strains.

Histopathology is used post-mortem to confirm NiV diagnosis in fatal cases. Virus isolation and neutralisation techniques are generally used for confirmation and are restricted to BSL-4 facilities.

The majority of international laboratories currently use in-house NiV assays, even though there exists a wide variation in the degree of test validation.

As the symptoms of NiV infection can mimic other encephalitic diseases, there is a higher risk of misdiagnosis, delayed treatment and fatality in severe cases. A shift from individual tests to multiplex panels can help to quickly identify or eliminate likely pathogens from a single specimen. Multiplex immunoassay platforms for differential diagnosis have been developed, which have also been used to detect henipavirus antibodies in fruit bats and pigs.

At the same time, point-of-care testing is yet to be developed for this WHO priority pathogen endemic to Southeast Asia.

Limited understanding of infection dynamics, difficulties in obtaining clinical specimens, the ecology of the wildlife reservoir and a lack of accurate surveillance data include the list of challenges hampering the efforts.

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