The demand for, and the promise of, quick accurate tools to diagnose tuberculosis, and to discover resistance to basic TB treatments, are based on a simple and seemingly irrefutable premise. Such tools, it has been pointed out, make early and effective treatment possible, benefiting both patients and public with faster and more frequent cures, and lowering transmission.
In theory, with an effective test, that should be the result. But the authors of a study published in PLOS One Friday point out, while data exists on the effectiveness of tests for TB drug resistance, data on the extent to which patients realize the benefits are harder to come by.
Studies have shown that the Xpert MTB/RIF tuberculosis test, which can detect tuberculosis bacteria missed by microscope examination, indicate resistance to the most common first treatments, and, with little expertise required to use, deliver results in about two hours, has hastened treatment for people with tuberculosis that is responsive to first-line drugs, the authors note. But, the authors add, they could find no published evidence that people with drug resistant strains of disease get that benefit. Aiming to fill that gap, they compared the time between diagnosis and starting treatment for patients with drug-resistant tuberculosis Cape Town, South Africa treatment centers that adopted World Health Organization recommendations first in 2008 to use the MDRTBPlus Line Probe Assay to identify drug resistance in samples from patients with tuberculosis, and then in 2011 to use the Xpert test to diagnose tuberculosis and determine its resistance to treatment. Their findings, detailed in A Comparison of Multidrug-Resistant Tuberculosis Treatment Commencement Times in MDRTBPlus Line Probe Assay and Xpert MTB/RIF-Based Algorithms in a Routine Operational Setting in Cape Town, highlight the realizable promise of quicker, simpler, more accessible diagnostic tools, but also highlight systemic gaps, questions, and obstacles.
Not surprisingly, they found the introduction of the quicker, newer, more comprehensive test came with shorter waits between diagnosis and treatments for patients with drug-resistant tuberculosis — with the median time cut by 25 days. But, surprisingly, they add, they still found a median wait between diagnosis and treatment of 17 days — a delay they call unacceptable. While accompanying health system strengthening may have contributed to the reduction in time to start treatment in recent years, they note, the remaining wait indicates more health system changes are needed. They also note that patient obstacles — work, transportation and resources — also may be adding to the wait, in some cases, between diagnosis and treatment. To realize the promise of improved diagnostic tools, they recommend exploring and addressing those gaps and obstacles.