Roadmap for the development of diagnostic test for bTB

What are we trying to achieve and why? What is the problem we are trying to solve?

A sensitive, specific, rapid, easy test to use, pen side test for livestock and wildlife – for direct detection of infected animals (including early stage or latent infection) or the presence of infection in animal products (meat and milk) or animal excreta.
Enable Differentiation between Infected and Vaccinated Animals (DIVA)
Why is a diagnostic test important and where is it needed? How can different diagnostics be developed and optimized for different purposes:

• Detection in live animals (wildlife/farmed – surveillance)
• Single shot test, same day
• Post-mortem surveillance
• Ante-mortem test in LMIC countries

What are the scientific and technological challenges
(knowledge gaps needing to be addressed)?

• Cost of test
• User friendliness
• Availability of reagents
• Evaluation, validation, and accreditation.
• Increased sensitivity implies that apparent prevalence underestimates true prevalence substantially.
• There are ISO-accredited lab Reference Methods (culture), no gold standard against which to compare; culture has well documented limitations.
• No equivalent to the human TB CRS (composite reference standard).
• Misinformation about what bTB test results mean.
• Optimal sample type?
• Turnaround times.
• Throughput.
• Challenge to develop a testing algorithm.

What approaches could/should be taken to address the research question?

Development of tests based on host responses that are more sensitive and specific than the tuberculin intradermal skin test for the detection of infection in live animals.
Development of tests for the detection of the organism or its metabolic (biomarker) products.
Explore advanced diagnostic technologies, such as next generation sequencing, proteomics, and metabolomics, to
identify new biomarkers and improve the sensitivity and specificity of bTB diagnostic tests.

Invest in research efforts to discover and validate novel biomarkers specific to bTB infection, disease progression, and
treatment response, leveraging omics technologies and comprehensive molecular profiling.
Consider CRISPR-based diagnostics.
Develop molecular methods, including genotyping and whole genome sequencing, to accurately differentiate and classify various bTB strains, including zoonotic and pandemic potential strains.
Invest in leveraging technologies such as isothermal amplification, lateral flow assays, and miniaturized lab-on-a-chip
devices for on-site bTB testing

What else needs to be done before we can solve this need?

Test validation in relation to sensitivity and specificity, Positive (PPV) and Negative Predictive Value (NPV) , yield and cost benefit analyses. Agree optimal sample type(s), protocols and timings.

Existing knowledge including successes and failures

• Current tuberculin skin test.
• Gamma interferon.
• Culture based detection.
• PCR based detection.
• AB based systems.
• Cepheid GeneXpert and Ultra used in human TB reference labs.
  Synthetic, defined purified protein derivative PPDs being trialled.