# Immunity to Non-Dengue Flaviviruses Impacts Dengue Virus Immunoglobulin G Enzyme-Linked Immunosorbent Assay Specificity in Cambodia

## TL;DR

A dengue virus test in Cambodia had lower accuracy due to immunity from other related viruses, suggesting the need for improved testing methods.

## Contribution

The study identifies non-dengue flavivirus immunity as a key factor reducing dengue IgG ELISA specificity in Cambodia.

## Key findings

- The dengue IgG ELISA had a specificity of 58%, much lower than previously reported 93%–100%.
- 46% of false positives had neutralizing antibodies against non-dengue flaviviruses, including 14% against West Nile virus.
- Adjusting the IgG ELISA cut point improved test accuracy in the population.

## Abstract

Seroprevalence studies are the standard for disease surveillance, and serology determined eligibility for the first dengue vaccine. Expanding flavivirus co-circulation and vaccination complicate testing. We evaluate the accuracy of a common dengue virus serological assay, examine immunity to non-dengue flaviviruses as a contributor to decreased performance, and assess whether alternative cut points may improve assay performance.

Children (n = 770) aged 2–9 years in Kampong Speu, Cambodia were enrolled in a prospective longitudinal study, and PanBio indirect dengue virus immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) was performed. Plaque reduction neutralization tests (PRNTs) using dengue viruses were performed on a subset to assess the accuracy of the IgG ELISA, and PRNTs with Zika, Japanese encephalitis, and West Nile viruses evaluated immunity to non-dengue flaviviruses. Receiver operating curve analysis identified an alternative cut point to improve IgG ELISA accuracy.

The dengue IgG ELISA had a lower specificity than previously reported (58% vs 93%–100%). Of those with false-positive IgG results, 46% had detectable neutralizing antibodies against other flaviviruses including 14% against West Nile virus. A higher IgG cut point improved the test accuracy in this population.

Physicians and public health authorities should be alert for West Nile in Cambodia. Immunity to non-dengue flaviviruses can impact dengue surveillance.

NCT03534245.

In this cohort of 770 Cambodian children aged 2–9 years, a dengue virus IgG ELISA had a lower specificity than previously reported (58% vs 93%–100%). Neutralizing antibodies against other flaviviruses contributed to this decreased accuracy and should be considered in dengue surveillance.