Background Crimean-Congo Haemorrhagic Fever (CCHF) is a life-threatening disease with a fatality rate ranging from 10% to 50%, and up to 80% in outbreaks. Despite its severity, there are no licensed drugs or vaccines available, and treatment options like Ribavirin are only effective if administered early. The current diagnostic method is slow, taking 2-5 days, which delays treatment, worsens patient outcomes, increases the risk of human-to-human transmission, and strains healthcare resources. Rapid diagnostic tests (RDTs) have been identified as a priority by the WHO to address these challenges.
Delays in diagnosis are particularly critical in regions such as Afghanistan and Pakistan, where suspected CCHF cases, especially among pregnant women, struggle to access emergency care until test results are available. The WHO R\&D Blueprint has emphasized the urgent need for point-of-care (POC) tests to reduce diagnosis time and improve patient management.
To meet this need, the Liverpool School of Tropical Medicine (LSTM) and Global Access Diagnostics (GADx) have developed an RDT prototype capable of detecting CCHF viral antigens. This prototype has demonstrated promising sensitivity and specificity, exceeding the WHO's target product profile (TPP) minimum requirements of \>80% sensitivity and \>90% specificity, with optimal performance defined as \>90% sensitivity and \>95% specificity. Initial tests in Türkiye in August 2024 showed the prototype achieving sensitivity of 81.2% in 38 prospective samples and 86.4% in 117 retrospective inactivated serum samples, with specificity between 95.5% and 98%.
Further testing in December 2024 with 770 frozen stored samples in Iraq and Türkiye yielded slightly lower performance, potentially due to the effects of freezing and thawing on sample integrity. We hypothesize that freezing alters gene expression, protein stability, and aggregation, impacting test accuracy. Therefore, additional testing with fresh, unfrozen samples is needed to confirm the RDT's reliability before progressing to clinical evaluation.
Aims This study aims to evaluate the RDT using 200 fresh samples collected during the 2025 CCHF season in Sivas and Samsun, Türkiye. If performance aligns with WHO TPP standards, a clinical trial involving 492 patients in CCHF-endemic regions of Türkiye is planned for 2026. The trial data will support regulatory submissions for CE IVDR and UKCA certification.
Methods Before launching the clinical trial, the investigators will conduct further diagnostic accuracy testing on 200 fresh samples (whole blood and serum) to ensure compliance with WHO TPP standards. These samples, pseudonymized and not used for patient management, will also undergo stability testing to assess the impact of storage conditions, including refrigeration for 72 hours (at Sivas site only) and freeze-thaw cycles.
By using optimized RDTs and fresh samples, we aim to improve sensitivity and specificity beyond previous results from December 2024. This study is critical for refining the test, ensuring its effectiveness, and providing essential data on device stability. Ultimately, this research will pave the way for a reliable, rapid diagnostic tool that can significantly enhance CCHF detection and patient outcomes in endemic regions.
