Where Does TBDX Fit Within the Spectrum of TB Diagnostic Technologies?

Even in this digital age of advanced healthcare diagnostic tools, developing nations around the globe continue to lose ground in the fight to control the TB pandemic.  For many reasons, not the least of which is loss of containment of the disease. Developed nations have invested heavily in research and development to develop new diagnostic technologies. Among those new technologies are the following:

  • Fluorescent microscopy (FM)
  • LED FM
  • Automated liquid culture (MGIT)
  • Microscopic-observation drug-susceptibility culture (MODS)
  • Nucleic acid amplification tests (NAAT) – GeneXpert falls within this category

These technologies represent remarkable advancements that will contribute greatly to slowing the growth of TB, however, none by themselves are a “silver bullet.”  .

Last week, with the introduction of TBDx at the Conference on Retrovirals and Opportunistic Infections (CROI), we added automated sputum microscopy to the fight.

As impressive as these technology achievements have been, TB remains a stubborn problem. In part this can be attributed to the fragmented nature of the healthcare delivery system in many countries. Laboratories may not exist within close proximity of the people with the illness.  Oftentimes people travel long distances to be tested and evaluated and, if the wait is long, will return home with no diagnosis. Lastly, these new technologies require a clinical operating environment and a stable supply of energy, something that is not always practical in rural or isolated settings. Even if the physical requirements are met, providing each clinic with state-of-the-art technologies has significant financial implications.

In part, whatever funding may be available for a national healthcare system must be spread across a multitude of illnesses, of which TB is just one. Many of these new TB technologies are expensive.  Deploying them to more local settings has, to date, been unaffordable. It has been estimated that to scale-up molecular diagnostic testing, in all the places where it could be used in India, would absorb the country’s entire healthcare budget.  MGIT, MODS, and NAAT culture tests can range from $17.00 – $25.00, pricing which might seem inexpensive to a developed country like the USA, but in highly burdened developing nations these per test costs are unattainable for the volume of diagnostic tests required.

World TB experts continually evaluate the landscape – technologies, costs, diagnostic performance, ability to deliver diagnosis closer to the point-of-care, and distributed versus centralized laboratory structures.  They exchange thoughts, concepts and data in an attempt to answer the most basic, fundamental question – how do we deliver the most timely, accurate, low-cost diagnostic capability to meet the demands of the disease without violating budgetary constraints? This was a question under consideration during the Q&A period of last week’s panel presentation. Following Dr. Gavin Churchyard’s presentation of the TBDx clinical trial results, he was asked where this technology fits within the spectrum of diagnostic technologies currently deployed.

“In India and China, where considerable focus remains on sputum microscopy, TBDx would be a technology that could reduce the workload by 50% or better. It can be an important screening tool that would focus human resources more appropriately on more difficult cases where a human could perform best. It can be used either in a large laboratory setting or, because of its modular design, could be used in a rural setting,” Dr. Churchyard noted.

Following the presentations and panel discussions the co-chair, Dr. Helen Ayres (Zambia) asked, “Are we where we want to be? How do we use these technologies in combination? Many are in central laboratories, but the problem is more local. How do we combine them not only in South Africa, but in countries like Zambia?”

Dr. Yukaki Manabe of the Johns Hopkins University Public School of Health responded.

“A diagnostic hub may be the way to go in the future, particularly in urban centers where quality control is an issue. I have to say I am very interested in Gavin’s presentation in terms of decreasing workflow by pooling specimens in one place, where you could put a person on a bus for a small amount of money in, say a place like Uganda, where you bring huge volumes to a specific place and put in tandem a good electrical system and a GeneXpert system, in Zambia for example, and first run automated sputum microscopy and run GeneXpert on others. It would require some retraining but a result could accompany the patient back on the bus and that could be a good solution in some clinical settings.”

In spite of medical technologies that can address a particular medical problem, oftentimes structural changes in how care is distributed, how processes and procedures are organized can do as much or more in improving medical outcomes, as relying solely on the use of the technology advancement. Much is true with TB diagnostic technologies. Changing how sputa is collected, how patients access clinical care, and how technologies can be centralized, using a business and transport model, would minimize the capital investment cost in hardware, allow all patients access to the best technologies, reduce the need for more laboratories and more trained personnel to continue to meet the growing demands.

The panelists were clear that we need to bring, in a cost-effective manner, the best technology that can solve a patient’s problem. It is likely that these efficiencies can occur where TBDx acts as a screening tool that culls through patient cases passing off to more expensive tests, only those that have been pre-qualified.

So, what are the efficiencies? How can you combine TBDx in tandem with the use of NAAT to provide the best diagnostic help with the lowest costs? This is a subject we have been discussing both inside and outside the company over the past several months.

In our next blog we will take you through the economics of combining two diagnostic tests, TBDx to identify those patient cases best qualified for further NAAT testing, and how this layered diagnostic approach will identify more quickly a higher number of positive TB cases, while at the same time illustrate how this lowers the per-positive-case expense for the health care system.

Benefits of this approach extend far beyond micro- economic savings.  At the macro-economic level an increase in positive case detection would ripple through the economy – less need for hospital stays, increased manpower productivity due to less work time lost, less need for economic subsidies to affected families, and most importantly, the potential to lower the transmission rate of the disease.

Until the next post, why not take a look at the CROI Presentation Video . If you are not interested in listening to all of the session presentations, fast forward to the 28th minute, listen to Dr. Churchyard’s presentation and the remaining dialogue among the panelists.

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