Use of Dried Blood Spots for Identifying Hepatitis E Infections in an Outbreak Setting.

Accurate and accessible diagnostics for hepatitis E virus (HEV) are essential for outbreak preparedness and surveillance, particularly in low-resource settings. Dried blood spots (DBS) are a scalable alternative to serum, but their diagnostic performance for HEV remains poorly characterised. Paired DBS and serum samples were collected from suspected HEV cases during an outbreak in Bentiu, South Sudan. HEV RNA was detected and quantified by RT-PCR, and anti-HEV IgM and IgG were measured by ELISA. DBS performance was compared to serum across assays, and associations between DBS positivity and serum viral load were analysed using logistic regression. Among 100 serum RT-PCR positive samples, 83 were positive by DBS (sensitivity 83.0%, 95% CI: 74.5-89.1), with reduced sensitivity at low viral loads (Ct > 30). All 48 serum RT-PCR negative samples were negative by DBS (specificity 100%, 95% CI: 92.6-100). DBS achieved 88.3% sensitivity (95% CI: 77.8-94.2) and 100% specificity (95% CI: 91.2-100) for IgM, while IgG sensitivity and specificity reached 95.0% (95% CI: 86.3-98.6) and 97.5%-100%, respectively. Results were consistent across DBS card types and age groups. DBS provide a practical complementary alternative to serum for HEV surveillance and outbreak investigations, particularly where conventional sampling and cold-chain transport are challenging. However, slightly reduced sensitivity at low viral loads and IgM detection limits their use as a stand-alone diagnostic approach for acute case detection Further optimisation of elution methods to increase analyte concentration, along with improved storage conditions, could enhance diagnostic sensitivity.