A Centre of Excellence for Biomedical Research and Training In Africa

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Validation and Integration of a new In-vitro Diagnostic test, the IFN-γ Release Immuno-Suspension Assay (IRISA) to improve diagnosis of Tuberculosis Meningitis – A multi-country study

Award Period: 2017-19

Funder: The Southern Africa Network for Biosciences (NEPAD SANBio)

BRTI (Zimbabwe) team

Team Lead   Dr Junior Mutsvangwa

Clinicians  Prof Hilda Mujuru (Paediatrician)

   Dr Wendy Chaka (Physician)

Research Nurse Edith Mpandaguta

Lab Scientist  Beauty Makamure

Multi- country Validation Team:

South Africa: Prof. Keertan Dheda (Principal Investigator) and Dr Phillipa Randall (Project       Manager): Lung Institute, UCT, Cape Town, South Africa

Zimbabwe: Dr. Junior Mutsvangwa (co-PI) Biomedical Research &Training       Institute, Harare, Zimbabwe

Malawi:  Dr. Marriot Nliwasa (co-PI) College of Medicine,        University of Malawi, Blantyre

Antrum Biotech:  Ms. Khilona Radia (CEO) Cape Town, South Africa (Commercial Partner)

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The goal of this project is to provide an affordable, accurate, diagnostic test for TBM for use in high TB burden countries


Aim

To validate the novel in-vitro diagnostic(IVD) test for TB meningitis and determine its placement in a rapid diagnostic algorithm thereby increasing prospects for commercialisation.


Scientific objectives 

  1. To determine the critical test cut-off value of gamma interferon levels in CSF for the diagnosis of TB meningitis in adults and children.

  2. To assess the sensitivity and specificity of the ELISA test for TB meningitis in adults and children.

  3. To convert the IVD test kit from being an innovative research product to a commercial     kit

Outcomes

  1. The critical test cut-off value of the new IVD in detecting TBM in adults and children

  2. Sensitivity, specificity and predictive values of the new IVD kit in detecting TBM adults and children

  3. A Product registration dossier

  4. Registration certificate for marketing the product


BACKGROUND

Tuberculosis (TB) has remained a public health crisis, particularly in sub-Saharan Africa where it is a leading cause of death 1, 2. Detection of TB and extra-pulmonary TB (EPTB; TB outside of the lungs) remains a major challenge 3. EPTB comprises 15% of TB though in HIV endemic countries this figure is closer to 35%.


Early diagnosis is the key to improving the health outcomes of this disease, but the current diagnostic tests have been optimised for Pulmonary TB and not Extra-pulmonary TB (EPTB)- TB Meningitis included.


The performance of current diagnostics when using EPTB fluid is sub-optimal due to their focus on the direct detection of the mycobacteria. Active tuberculosis involving serosal surfaces, the meninges, and sterile fluid is typically pauci-bacillary. For example, using pleural fluid smear microscopy and culture positivity rates are ~5% and 40%, respectively and culture results only become available in a period up to 8 weeks. GeneXpert MTB/RIF and GeneXpert MTB/RIF Ultra perform poorly in this setting (sensitivity in pleural fluid <50%). Thus, clinicians use supplementary tests such as immunodiagnostic assays to aid the diagnosis of EPTB. Biomarkers like adenosine deaminase (ADA) have a poor specificity between ~ 60 to 70% in pleural TB (cut point of 30 IU/L) and a sub-optimal negative predictive value (NPV). Diagnosis of EPTB is problematic and challenging with under- diagnosis (poor sensitivity of existing tests) – high morbidity and mortality……..  

….and frequent overtreatment (poor specificity) resulting in unnecessary drug toxicity, cost, patient discomfort, and economic consequences.

By contrast, unstimulated interferon gamma (IFN-γ) has shown promising optimal performance in EPTB compartments as this assay is different from interferon gamma release assays (IGRAs) because it does not require overnight stimulation with mycobacterial proteins or peptides prior to testing.

Test attributes

  • Same day diagnosis

  • 2-hour processing time) using sterile fluid (i.e. pleural, pericardial, peritoneal or cerebrospinal fluid).

  • Flexibility in that:

    • test can be done for single patient or any number up to 41 patients’ samples at a time

    • Single test platform for all TB serositis (Pleural, pericardial, peritoneal fluids) including TB meningitis

  • No need for overnight stimulation

  • Use of routine open lab system – only ELISA reader needed (No sophisticated supplier dependant platforms) – can easily be decentralised

  • Uses small volumes of CSF (50ul)- hence applicable to children

  • Minimal to no sample processing


VALIDATION STUDIES

IRISA-TB and the detection unstimulated IFNγ as a means to diagnose EPTB has been subjected to internal and external validations. Its’ performance has been compared to Xpert MTB/RIF, Xpert Ultra and/or ADA in diagnosing pleural TB (3 studies), pericardial TB (2 studies; 1 complete and the other on-going), peritoneal TB (1 study) and TB meningitis (2 studies; 1 complete and the other an external validation involving sites in South Africa, Zimbabwe, Malawi and Zambia). The analysis for the multi-country validation study entitled ‘Validation and integration of a new test to improve diagnosis of tuberculous meningitis’ encompasses a cohort of 1203 of which 537 CSF samples have been applied to IRISA-TB (South Africa = 151, Zambia = 80, Malawi = 216 and Zimbabwe = 184). Confirmed TB meningitis was defined as those with at least 1 microbiological positive test (culture or Xpert MTB/RIF or Xpert Ultra), individuals were initiated onto TB treatment and improved after 2 months. Confirmed non-TBM with those where all microbiological tests were negative, Gram stain or CLAT test positive, given an alternative diagnosis and TB treatment was not initiated. At a cut-off point of 13.5pg/ml, the sensitivity and specificity of the IRISA-TB is 76% and 92%, respectively.


PROGRESS SO FAR

  • Package insert and product dossier are now now in place-Kit registration and finalization of kit cost are work in progress

  • Product launch in the participating countries- plans at advanced stages and this is includes:

  • Stakeholders engagement for placement of kit  in the national TBM testing algorithms

  • Market entry



The Market:

The primary beneficiaries are patients with symptoms suggestive of TB and EPTB, who currently face delayed access to appropriate treatment due to the lack of a reliable diagnosis. Therefore, the potential customers are health providers (hospitals and clinics) in the public and private sector that operate in countries with a high burden of TB. The WHO have identified 22 of these high-burden countries including South Africa, many African countries, India and China. Due to the vertical nature of TB control programs, the vehicle for accessing the public sector target market in most low-income countries will be the Ministry of Health and/or the NTPs. Influencers of the market from the charitable and NGO sectors and activist who campaign for better TB care (MSF Access campaign, TB Alert, Treatment Action Group, RESULTS) are being informed of the accumulated data. Links between members of the project team and these organisations already exist.

The product/s are likely to provide economic benefits to the health provider as it will be cheaper than the current rapid (less sensitive) GeneXpert MTB/RIF test. Socioeconomic benefits will likely accrue from averting avoidable morbidity and mortality due to the increased access to curative treatment.



IMPACT OF THE STUDY and PRODUCT TO ZIMBABWE

  1. The study has provided

  1. the local research team with skills on how to move a research output to commercialization

  2. an opportunity to network with new partners for such future activities

  3. an opportunity for local team for consultancy on use of kit

  1. The kit will provide motivation for the Zimbabwean clinicians to request for TB meningitis lab processing given that the (IRISA) is the first assay optimised specifically for ETB(CSF) and Serositis with proven positive performance illustrated through a robust inter-country robust validation (Zimbabwe included).