Diagnostic performance of molecular and serological markers for hepatitis E virus and Toxoplasma gondii coinfection across gestation in HIV-positive pregnant women

Accurate identification of recent hepatitis E virus (HEV) and Toxoplasma gondii infections during pregnancy is essential for clinical management, yet diagnostic performance data in HIV-positive populations remain limited. We evaluated serological and molecular diagnostic approaches for detecting recent coinfection across gestation. In a prospective cohort of 780 HIV-positive pregnant women (CD4+ 200–400 cells/µL) in central Nigeria, we performed serial HEV and T. gondii IgG/IgM testing using recomLine immunoblot assays. A validation subset (n=80) underwent HEV RNA detection by RT-qPCR and T. gondii IgG avidity testing. Diagnostic performance was calculated using molecular and avidity markers as reference standards. HEV IgM demonstrated 100% sensitivity (34/34) and 69.6% specificity for detecting HEV RNA-positive viraemia, the latter reflecting post-viraemic IgM persistence rather than serological false positivity, with 100% negative predictive value. Among IgM-positive participants, 70.8% (34/48) had detectable HEV RNA (mean Ct 31.6±1.8). T. gondii IgM showed 100% concordance with low/intermediate avidity results, achieving 100% sensitivity and specificity for recent infection classification. Coinfection incidence increased from 1.9 to 7.8 per 100 person-months across gestation (adjusted HR 4.12, 95% CI 2.47–6.87). Dual IgM-positive cases showed 80% molecular/avidity confirmation of recent coinfection. Coinfection was associated with substantially elevated risks of adverse foetomaternal outcomes, including preterm birth (aRR 2.89, 95% CI 1.94–4.31), low birth weight (aRR 3.12, 95% CI 2.18–4.47), and perinatal mortality (aRR 4.17, 95% CI 2.04–8.52), all p<0.001. Serological screening shows a very high negative predictive value, which is helpful in ruling out recent infections of HEV and T. gondii in HIV-positive pregnant women. If IgM antibodies are found, further testing using molecular or avidity-based methods is necessary.