Tuberculosis (TB), an infectious disease caused by the bacterium Mycobacterium tuberculosis (MTB), mainly affects the lungs, though other parts of the body can be affected. Drug resistant TB occurs if the TB bacteria that the person is infected with do not respond to at least one of the main TB drugs. Healio recently reported on a new point-of-care test that can detect resistance to important treatments for multidrug-resistant TB. According to the researchers, clinicians could use this test to determine the right treatment for patients with multidrug-resistant TB infections.
There are two main types of drug resistant TB - MDR (multidrug resistant) TB and XDR (extensively drug resistant) TB. According to the World Health Organization (WHO), there were an estimated 480,000 incident cases of MDR-TB worldwide in 2015. A recent research study published in The New England Journal of Medicine found that an investigational assay, - Xpert MTB/RIF Ultra - can accurately detect drug-resistant tuberculosis infections. This new point-of-care test is an updated version of Cepheid's Xpert MTB/RIF assay.
Developed at the lab of David Alland MD, the chief of infectious diseases and associate dean of clinical research at Rutgers New Jersey Medical School, this assay is meant to be used as a reflex test only in patients who test positive for TB using one of two assays made by Cepheid. It looks for resistance to several important treatments for multidrug-resistant TB such as isoniazid as well as the fluoroquinolones moxifloxacin and ofloxacin and the aminoglycosides amikacin and kanamycin. It is the only rapid point-of-care test to facilitate evidence-based treatment selection for patients with rifampin-resistant TB.
In addition to speeding up the detection of drug-resistant TB, researchers say new assay could provide several benefits, such as:
- Getting patients on potentially life-saving treatment
- Promoting the implementation of infection control procedures, and
- Improving triage into or out of short-course multidrug-resistant treatment
The study involved tracking more than 400 adults with symptoms of TBfor a year. Up to 308 had TB infections confirmed by a culture and were included in the main analysis for drug-susceptibility. The new investigational assay was successful in detecting 98% of TB infections, same as the Xpert MTB/RIF assay. The specificity was 99.6% or greater for all of the study drugs when compared with DNA sequencing, exceeding WHO's specificity target of 98%.
It was also effective at identifying patients who were microbiologically eligible or ineligible for a shortened treatment regimen for TB resistance based on their infection's response to fluoroquinolones or aminoglycosides. The team speculates that the assay can be used to triage patients toward treatment centers that are equipped to conduct comprehensive drug-susceptibility testing and have experience treating highly drug-resistant TB.