While developing an ultrasensitive test for the detection of Mycobacterium tuberculosis DNA (TB-DNA), researchers from Boston University have unexpectedly found a high prevalence of the molecular marker in U.S.-born patients hospitalized in Boston.
“We began this research with the intent of sourcing respiratory samples to support the ongoing development of a new molecular assay for TB,” said Guillermo Madico, MD, PhD, scientist at Boston University’s National Emerging Infectious Diseases Laboratories (NEIDL) and co-inventor of the TOP TB assay. “What we found was completely unexpected. Our ultrasensitive test is detecting Mycobacterium tuberculosis DNA in patients who are unlikely to be diagnosed with TB using current methods. This opens the possibility that there could be thousands of Americans infected with forms of tuberculosis disease that remain hidden from our current diagnostic tools—putting them at risk of developing more serious complications or potentially transmitting the disease to others.”
In 2022, there were over 8000 reported cases of TB in the United States, over 600 TB-related deaths, and an estimated 13 million people with Mycobacterium tuberculosis infection. Although incidence has steadily decreased in the U.S., the rate of decline is too slow to meet the ambitious World Health Organization strategy to end the global TB epidemic by 2035.
One threat to the global elimination goal is a gap in the detection of paucibacillary TB disease—a type of TB characterized by a low concentration of M. tuberculosis bacilli in samples that often results in false negative test results.
To improve detection, Madico and colleagues developed an ultrasensitive molecular assay developed at Boston University called the Totally Optimized PCR (TOP) TB assay, which targets a gene involved in M. tuberculosis cell wall assembly.
During the development process, the researchers conducted three separate clinical studies involving 297 patients from Boston hospitals.
Across the studies, the TOP TB assay detected TB DNA in 12–16% of samples—a rate far higher than expected given Boston’s low TB incidence rate. Of note, most TB DNA-positive patients tested negative on standard TB infection tests (tuberculin skin tests or interferon-gamma release assays), and the researchers hypothesize that the findings “indicate the existence of a paucibacillary form of TB that remains unrecognized and is not detectable using current diagnostic tools.”
During the study, there were three patients diagnosed with acute chest syndrome, a life-threatening complication of sickle cell disease, all of whom tested positive for TB DNA.
The researchers point out in Nature Communications that this “previously unrecognized association” has potential implications for clinical care in the U.S. and many other settings.
“These findings suggest we may be missing a significant burden of TB disease, particularly in older Americans and in patients with certain underlying conditions,” said Edward Jones-López, MD, who co-led the study while at Boston Medical Center and Boston University Chobanian & Avedisian School of Medicine. “Most concerning is the potential association with acute chest syndrome in sickle cell patients. If confirmed and expanded upon in larger studies, this finding could lead to better health outcomes for patients with this potentially life-threatening condition.”
The researchers emphasize that their preliminary findings require confirmation in larger, prospective multicenter studies that include comprehensive clinical, radiological, immunological, and microbiological correlation. However, they argue the evidence warrants immediate dissemination given potential implications for medical care and public health.
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