Diagnostic performance and kinetics of hepatitis E viral RNA and IgM antibody test positivity in a genotype 1 outbreak in South Sudan

BACKGROUND

Diagnostics are essential for understanding hepatitis E epidemiology, but the field performance of available tests remains unclear. We evaluated the performance of PCR, IgM ELISA, and the Assure HEV IgM rapid diagnostic test (RDT) during a HEV genotype 1 outbreak and assessed the duration of viremia and antibodies responses.

METHODS

We used data from enhanced surveillance at a health facility in Bentiu internally displaced persons camp, South Sudan (March-December 2022). As part of a vaccine effectiveness study suspected hepatitis E cases underwent testing with all three diagnostics at enrolment with a follow-up sample. We used a latent class model to estimate test performance and accelerated failure time models to estimate time from jaundice onset to a negative test for PCR and ELISA.

FINDINGS

Among 893 suspected cases, test sensitivity declined with time from jaundice onset. Within 30 days of jaundice onset, PCR sensitivity was 73% (95% Credible Interval (CrI) 27, 90), compared to 86% for RDT (95% CrI: 74, 93), and 95% for ELISA (95% CrI: 91, 98). Specificity was high across tests: PCR at 98% (95% CrI: 98, 99), RDT at 95% (95% CrI: 93, 96), and ELISA at 95% (95% CrI: 93, 96). Median time from jaundice onset to negative test was 19 days (95% CI: 17, 21) for PCR and 113 days (95% CI: 87, 163) for ELISA.

INTERPRETATION

The Assure IgM RDT showed higher sensitivity for identifying hepatitis E than PCR and similar specificity to IgM ELISA, supporting its use in surveillance. Care seeking delays can greatly influence the interpretation of diagnostic tests.