Recent advances in the development and evaluation of molecular diagnostics for Ebola virus disease

Head-to-head comparison of diagnostic accuracy of four Ebola virus disease rapid diagnostic tests versus GeneXpert® in eastern Democratic Republic of the Congo outbreaks: a prospective observational study

BACKGROUND

Ebola virus disease (EVD) outbreaks have emerged in Central and West Africa. EVD diagnosis relies principally on RT-PCR testing with GeneXpert®, which has logistical and cost restrictions at the peripheral level of the health system. Rapid diagnostic tests (RDTs) would offer a valuable alternative at the point-of-care to reduce the turn-around time, if they show good performance characteristics. We evaluated the performance of four EVD RDTs against the reference standard GeneXpert® on stored EVD positive and negative blood samples collected between 2018 and 2021 from outbreaks in eastern Democratic Republic of the Congo (DRC).

METHODS

We conducted a prospective and observational study in the laboratory on QuickNavi-Ebola™, OraQuick® Ebola Rapid Antigen, Coris® EBOLA Ag K-SeT, and Standard® Q Ebola Zaïre Ag RDTs using left-over archived frozen EDTA whole blood samples. We randomly selected 450 positive and 450 negative samples from the EVD biorepositories in DRC, across a range of GeneXpert® cycle threshold values (Ct-values). RDT results were read by three persons and we considered an RDT result as "positive", when it was flagged as positive by at least two out of the three readers. We estimated the sensitivity and specificity through two independent generalized (logistic) linear mixed models (GLMM).

FINDINGS

476 (53%) of 900 samples had a positive GeneXpert Ebola result when retested. The QuickNavi-Ebola™ showed a sensitivity of 56.8% (95% CI 53.6-60.0) and a specificity of 97.5% (95% CI 96.2-98.4), the OraQuick® Ebola Rapid Antigen test displayed 61.6% (95% CI 57.0-65.9) sensitivity and 98.1% (95% CI 96.2-99.1) specificity, the Coris® EBOLA Ag K-SeT showed 25.0% (95% CI 22.3-27.9) sensitivity and 95.9% (95% CI 94.2-97.1) specificity, and the Standard® Q Ebola Zaïre Ag displayed 21.6% (95% CI 18.1-25.7) sensitivity and 99.1% (95% CI 97.4-99.7) specificity.

INTERPRETATION

None of the RDTs evaluated approached the "desired or acceptable levels" for sensitivity set out in the WHO target product profile, while all of the tests met the "desired level" for specificity. Nevertheless, the QuickNavi-Ebola™ and OraQuick® Ebola Rapid Antigen Test demonstrated the most favorable profiles, and may be used as frontline tests for triage of suspected-cases while waiting for RT-qPCR confirmatory testing.

FUNDING

Institute of Tropical Medicine Antwerp/EDCTP PEAU-EBOV-RDC project.

Immunosensors-The Future of Pathogen Real-Time Detection

Pathogens and their toxins can cause various diseases of different severity. Some of them may be fatal, and therefore early diagnosis and suitable treatment is essential. There are numerous available methods used for their rapid screening. Conventional laboratory-based techniques such as culturing, enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) are dominant. However, culturing still remains the "gold standard" for their identification. These methods have many advantages, including high sensitivity and selectivity, but also numerous limitations, such as long experiment-time, costly instrumentation, and the need for well-qualified personnel to operate the equipment. All these existing limitations are the reasons for the continuous search for a new solutions in the field of bacteria identification. For years, research has been focusing on the use of immunosensors in various types of toxin- and pathogen-detection. Compared to the conventional methods, immunosensors do not require well-trained personnel. What is more, immunosensors are quick, highly selective and sensitive, and possess the potential to significantly improve the pathogen and toxin diagnostic-processes. There is a very important potential use for them in various transport systems, where the risk of contamination by bioagents is very high. In this paper, the advances in the field of immunosensor usage in pathogenic microorganism- and toxin-detection, are described.

A Systematic Review on Suitability of Molecular Techniques for Diagnosis and Research into Infectious Diseases of Concern in Resource-Limited Settings

Infectious diseases significantly impact the health status of developing countries. Historically, infectious diseases of the tropics especially have received insufficient attention in worldwide public health initiatives, resulting in poor preventive and treatment options. Many molecular tests for human infections have been established since the 1980s, when polymerase chain reaction (PCR) testing was introduced. In spite of the substantial innovative advancements in PCR technology, which currently has found wide application in most viral pathogens of global concern, the development and application of molecular diagnostics, particularly in resource-limited settings, poses potential constraints. This review accessed data from sources including PubMed, Google Scholar, the Web of Knowledge, as well as reports from the World Health Organization’s Annual Meeting on infectious diseases and examined these for current molecular approaches used to identify, monitor, or investigate some neglected tropical infectious diseases. This review noted some growth efforts in the development of molecular techniques for diagnosis of pathogens that appear to be common in resource limited settings and identified gaps in the availability and applicability of most of these molecular diagnostics, which need to be addressed if the One Health goal is to be achieved.

Field performance of three Ebola rapid diagnostic tests used during the 2018-20 outbreak in the eastern Democratic Republic of the Congo: a retrospective, multicentre observational study

BACKGROUND

The Democratic Republic of the Congo has confronted 13 outbreaks of Ebola virus disease since 1976. Rapid diagnostic tests (RDTs) detecting viral antigens have been developed to circumvent difficulties encountered with RT-PCR for diagnosis in remote low-resource settings, but there is still uncertainty about their performance characteristics and usability during outbreaks. We aimed to assess the field performance of three antigen detection RDTs compared with the gold-standard Cepheid GeneXpert Ebola assay results.

METHODS

We conducted a retrospective, multicentre observational study using complete and de-identified databases of five mobile laboratories (managed by the Institut National de Recherche Biomédicale) to assess the performance of three Ebola virus disease RDTs (QuickNavi-Ebola, OraQuick Ebola Rapid Antigen Test, and Coris EBOLA Ag K-SeT rapid test) run on blood samples of patients with suspected Ebola virus disease in direct comparison with the Cepheid GeneXpert Ebola assay reference test during the 2018-20 outbreak in the eastern Democratic Republic of the Congo. We estimated the sensitivity and specificity of each test through generalised linear mixed models against the GeneXpert Ebola assay reference test and corrected for cycle threshold value and random site effects.

FINDINGS

719 (7·9%) of 9157 samples had a positive GeneXpert Ebola assay result. The QuickNavi-Ebola RDT had a sensitivity of 87·4% (95% CI 63·6-96·8) around the mean cycle threshold value and a specificity of 99·6% (99·3-99·8). The OraQuick Ebola Rapid Antigen Test had a sensitivity of 57·4% (95% CI 38·8-75·8) and specificity of 98·3% (97·5-99·0), and the Coris EBOLA Ag K-SeT rapid test had a sensitivity of 38·9% (23·0-63·6) against the GeneXpert Ebola assay reference and specificity of 97·4% (85·3-99·6). The QuickNavi-Ebola RDT showed a robust performance with good sensitivity, particularly with increasing viral loads (ie, low cycle threshold values), and specificity.

INTERPRETATION

The three RDTs evaluated did not achieve the desired sensitivity and specificity of the WHO target product profile. Although the RDTs cannot triage and rule out Ebola virus infection among clinical suspects, they can still help to sort people with suspected Ebola virus disease into high-risk and low-risk groups while waiting for GeneXpert Ebola assay reference testing.

FUNDING

None.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

Ultrasensitive point-of-care immunoassay for secreted glycoprotein detects Ebola infection earlier than PCR

Ebola virus (EBOV) hemorrhagic fever outbreaks have been challenging to deter due to the lack of health care infrastructure in disease-endemic countries and a corresponding inability to diagnose and contain the disease at an early stage. EBOV vaccines and therapies have improved disease outcomes, but the advent of an affordable, easily accessed, mass-produced rapid diagnostic test (RDT) that matches the performance of more resource-intensive polymerase chain reaction (PCR) assays would be invaluable in containing future outbreaks. Here, we developed and demonstrated the performance of a new ultrasensitive point-of-care immunoassay, the EBOV D4 assay, which targets the secreted glycoprotein of EBOV. The EBOV D4 assay is 1000-fold more sensitive than the U.S. Food and Drug Administration-approved RDTs and detected EBOV infection earlier than PCR in a standard nonhuman primate model. The EBOV D4 assay is suitable for low-resource settings and may facilitate earlier detection, containment, and treatment during outbreaks of the disease.

The Use of Near-Infrared Light-Emitting Fluorescent Nanodiamond Particles to Detect Ebola Virus Glycoprotein: Technology Development and Proof of Principle

Background

There is a dire need for rapid diagnostic tests of high sensitivity, efficiency, and point-of-test reporting capability to mitigate lethal viral epidemic outbreaks.

Purpose

To develop a new operating system within the lateral flow assay (LFA) format for Ebola virus (EBOV), based on fluorescent nanodiamond particles (FNDP) nitrogen vacancy (NV) emitting near-infrared (NIR) light. Specifically, we aimed to detail technical issues and the feasibility of mobilizing FNDP-NV on nitrocellulose membranes (NCM) and capturing them at test and control lines.

Methods

FNDP-NV-200nm, 400nm or 800nm were linked to anti-EBOV glycoprotein (GP) monoclonal antibodies (mAb) and tested for LFA performance by monitoring NIR emissions using an in vivo imaging system or optoelectronic device (OED). Anti-EBOV recombinant glycoprotein (GP) humanized mAb c13C6 was linked to FNDP-NV-200nm for the mobile phase; and a second anti-GP mouse mAb, 6D8, was printed on NCM at the test line. Goat anti-human IgG (GAH-IgG) served as a nonspecific antibody for conjugated FNDP-NV-200nm at the control line.

Results

FNDP-NV-200nm-c13C6 specifically and dose-dependently bound to recombinant EBOV GP in vitro and was effectively captured in a sandwich configuration at the test line by mAb 6D8. FNDP-NV-200nm-c13C6 was captured on the control line by GAH-IgG. The OED quantitative analysis of NIR (obtained in less than 1 minute) was further validated by an in vivo imaging system.

Conclusion

FNDP-NV-200nm performance as a reporter for EBOV GP rapid diagnostic tests suggests an opportunity to replace contemporary visual tests for EBOV GP and other highly lethal viral pathogens. Mobile, battery-operated OED adds portability, quantitative data, rapid data collection, and point-of-test reporting capability. Further development of FNDP-NV-200nm within a LFA format is justified.

A flexible format LAMP assay for rapid detection of Ebola virus

BACKGROUND

The unprecedented 2013/16 outbreak of Zaire ebolavirus (Ebola virus) in West Africa has highighted the need for rapid, high-throughput and POC diagnostic assays to enable timely detection and appropriate triaging of Ebola Virus Disease (EVD) patients. Ebola virus is highly infectious and prompt diagnosis and triage is crucial in preventing further spread within community and healthcare settings. Moreover, due to the ecology of Ebola virus it is important that newly developed diagnostic assays are suitable for use in both the healthcare environment and low resource rural locations.

METHODOLOGY/PRINCIPLE FINDINGS

A LAMP assay was successfully developed with three detection formats; a real-time intercalating dye-based assay, a real-time probe-based assay to enable multiplexing and an end-point colourimetric assay to simplify interpretation for the field. All assay formats were sensitive and specific, detecting a range of Ebola virus strains isolated in 1976-2014; with Probit analysis predicting limits of detection of 243, 290 and 75 copies/reaction respectively and no cross-detection of related strains or other viral haemorrhagic fevers (VHF's). The assays are rapid, (as fast as 5-7.25 mins for real-time formats) and robust, detecting Ebola virus RNA in presence of minimally diluted bodily fluids. Moreover, when tested on patient samples from the 2013/16 outbreak, there were no false positives and 93-96% of all new case positives were detected, with only a failure to detect very low copy number samples.

CONCLUSION/SIGNIFICANCE

These are a set of robust and adaptable diagnostic solutions, which are fast, easy-to-perform-and-interpret and are suitable for use on a range of platforms including portable low-power devices. They can be readily transferred to field-laboratory settings, with no specific equipment needs and are therefore ideally placed for use in locations with limited resources.

Ebola Virus Disease: Epidemiology, Clinical Features, Management, and Prevention

Ebola virus disease (EVD) is a deadly zoonotic disease caused by the Ebola virus. There is no specific treatment approved for EVD. Supportive care and management of complications are mainstays of treatment. Effective outbreak control requires a multidisciplinary team effort applying case management, infection prevention and control practices, surveillance and contact tracing, a good laboratory service, safe and dignified burials, and social and community mobilization. This article highlights the epidemiology, clinical features, diagnosis, management, and prevention of EVD. The emerging diagnostic technologies, rapid viral characterization, geospatial mapping of EVD transmission, and new treatments and vaccines are discussed.

Treatment of Ebola-related critical illness

PURPOSE

To explore contemporary clincial case management of patients with Ebola virus disease.

METHODS

A narrative review from a clinical perspective of clinical features, diagnostic tests, treatments and outcomes of patients with Ebola virus disease.

RESULTS

Substantial advances have been made in the care of patients with Ebola virus disease (EVD), precipitated by the unprecedented extent of the 2014-2016 outbreak. There has been improved point-of-care diagnostics, improved characterization of the clinical course of EVD, improved patient-optimized standards of care, evaluation of effective anti-Ebola therapies, administration of effective vaccines, and development of innovative Ebola treatment units. A better understanding of the Ebola virus disease clinical syndrome has led to the appreciation of a central role for critical care clinicians-over 50% of patients have life-threatening complications, including hypotension, severe electrolyte imbalance, acute kidney injury, metabolic acidosis and respiratory failure. Accordingly, patients often require critical care interventions such as monitoring of vital signs, intravenous fluid resuscitation, intravenous vasoactive medications, frequent diagnostic laboratory testing, renal replacement therapy, oxygen and occasionally mechanical ventilation.

CONCLUSION

With advanced training and adherence to infection prevention and control practices, clinical interventions, including critical care, are feasible and safe to perform in critically ill patients. With specific anti-Ebola medications, most patients can survive Ebola virus infection.