Performance Compared for Three Ebola Rapid Diagnostic Tests

Ebola is a rare but deadly virus that causes fever, body aches, and diarrhea, and sometimes bleeding inside and outside the body. As the virus spreads through the body, it damages the immune system and organs. Ultimately, it causes levels of blood-clotting cells to drop.

Diagnosing Ebola virus disease (EVD) shortly after infection can be difficult. Early symptoms of EVD such as fever, headache, and weakness are not specific to Ebola virus infection and often are seen in patients with other more common diseases, like malaria and typhoid fever. Polymerase chain reaction (PCR) is one of the most commonly used diagnostic methods because of its ability to detect low levels of Ebola virus.

An international team of scientists collaborating with Columbia University (New York, NY, USA) evaluated the three rapid diagnostic Tests (RDTs) in 109 Ebola-positive and 96 Ebola-negative stored serum samples collected during the outbreak in Guinea in 2014/15, and tested by real-time polymerase chain reaction (RT-PCR). Sensitivity, specificity, and overall percent agreement were calculated for each RDT using RT-PCR as a reference standard, stratified by Ct value ranges.

All tests evaluated in the study used the Dual Path Platform (DPP; Chembio Diagnostic Systems, Medford, NY, USA) technology, which consists of an immunochromatographic test cartridge and a small, battery-operated reflectance reader. The DPP Fever Panel Antigen System (the “Fever Panel Test”) is a multiplex assay detecting Plasmodium falciparum (HRP2), pan-Plasmodium (pLDH), and protein antigens specific for Lassa, Pan-Ebola (Zaire, Sudan, Bundibugyo), Marburg, Dengue, Chikungunya, and Zika Viruses. The DPP Ebola Antigen System (the “Ebola Test”) tests for Ebola Zaire antigen, and the DPP Ebola-Malaria Antigen duplex system (the “Ebola-Malaria Test”) detects Ebola Zaire antigen, Plasmodium falciparum (HRP2), and pan-Plasmodium (pLDH). All tests are qualitative and detect the VP40 antigen, which is specific to Ebola.

The investigators reported that all tests performed with high accuracy on samples with low Ct value (high viral load). The Fever Panel test performed with the highest accuracy, with a sensitivity of 89.9% and specificity of 90.6%. The Ebola and Ebola-Malaria tests performed comparably to each other: sensitivity was 77.1% and 78% respectively, and specificity was 91.7% for the Ebola test and 95.8% for the Ebola-Malaria test.

The authors concluded that their study had evaluated the accuracy of three novel rapid diagnostic tests for Ebola. The tests may have significant public health relevance, particularly the Fever Panel test, which detects seven pathogens including Ebola. Given limitations to the study resulting from uncertain sample quality, further evaluation is warranted. All tests performed with highest accuracy on samples with low Ct value (high viral load), and the data presented suggests that these RDTs may be useful for point-of-care diagnosis of cases in the context of an outbreak. The study was published on September 15, 2020 in the journal BMC Infectious Diseases.