A promising new TB diagnostic test, soon to enter Phase II trials in South Africa, could make screening for the disease faster, cheaper and more accurate than anything currently on the market, reports IRIN/PlusNews
Signature Mapping TBDx, an automated diagnostic solution that uses sophisticated detection algorithms to identify TB under microscopy in sputum samples, recently concluded Phase I clinical evaluations at South Africa’s National Health Laboratory Service(NHLS) Recheck Program. Phase II clinical trials are set to begin early this year.
SM TBDx takes digital pictures of sputum samples and searches those images for TB’s signature structural “fingerprint.” The test works on the same principles as airport scanners, which search digital images of luggage for the structural fingerprint of plastic explosives.
According to David Clark, deputy CEO of the Aurum Institute the health research organization partnering with the NHLS to develop the tool, SM TBDx is the first TB diagnostic to combine advanced imaging technology with digital microscopy. If approved for use, the automated technology could dramatically reduce the labor involved in diagnosing TB. Guardian Technologies International, the test’s maker, was invited by the Government of India to present SM TBDx to a group of government ministers last October.
By automating the diagnostic process, SM TBDx obviates the need for skilled lab technicians; the test can be operated by personnel with no special skills and can run independently around the clock. And the test appears to be more efficient than conventional methods; a prototype has already proven 10 percent more effective at identifying TB bacilli than laboratory technicians hunched over a microscope.
Sputum microscopy, the most commonly used TB diagnostic test, relies on technology first developed by Robert Koch, the German physicist who discovered TB more than 100 years ago. In recent years, a number of newer and more sophisticated genetic TB diagnostics have come on the market, but all have their limitations, and the need remains for a rapid, cost-effective, and highly accurate method of diagnosing both latent and active TB infection (1).
SM TBDx may well fulfill those criteria. But the technology has yet to be costed, and despite promising signs that the test will be able to increase lab productivity and improve diagnosis, determining cost-effectiveness is a particular challenge for TB tests. There are currently no widely accepted standards for evaluating the costs of a TB test, and few studies have investigated the issue. (2)
Declaring, as PlusNews does, that the test could “revolutionise TB diagnosis” may be premature, especially given that rollout on a national level would not occur for at least another 3 years. But if, as its makers say, the SM pathology platform can be applied to other laboratory-diagnosed diseases, such as malaria, leprosy and cancer, this may be just the beginning of the good news.
1. Pai M et al. (2009). Novel and improved technologies for tuberculosis diagnosis: progress and challenges. Clin Chest Med; 30(4):701-716.
2. Sohn H. et al. (2009) TB diagnostic tests: how do we figure out their costs? Expert Rev Anti Infect Ther; 7(6):723-733.