Portable test could help millions with limited access to healthcare
Diagnosing tuberculosis – the world’s deadliest infectious disease – with minimal training and without expensive laboratory infrastructure could now be a reality for millions of people.
A portable device using $4 tests detects tuberculosis, or TB, from tongue swabs in just 30 minutesreport the researchers on April 29 in the New England Journal of Medicine. THE The World Health Organization recommended the test in March, the first official approval of a TB test that can be used at community sites without laboratories and with minimal technical expertise.
The recommendation “opens the door to getting accurate molecular testing for TB in the clinics where most people with TB present,” says Adithya Cattamanchi, a pulmonologist at the University of California, Irvine.
Antibiotics can cure tuberculosis, but among the more than 10 million people who suffer from the disease each year, more than a quarter remain undiagnosed or untreated. Smear microscopy, used for about 150 years, tests phlegm to detect the type of bacteria that causes infections like tuberculosis. This test determines tuberculosis within 24 hours, but at least 1 in 4 peopleincluding children, people with HIV, and the elderly, cannot produce phlegm adequately. Microscopic examination of smears is also lacking more than 40 percent of tuberculosis cases. Due to the limitations of microscopy, the WHO recommends diagnostics that generate copies of trace DNA from the bacteria that causes tuberculosis. These diagnostics can detect disease within hours, but require expensive laboratory infrastructure.
In contrast, the portable device, called MiniDock MTB, is “designed to work anywhere: a rural clinic, a community health post, even outdoors,” leveraging about a decade of research on oral swabs for tuberculosis, Cattamanchi says. The entire setup works with a power bank or wall power supply, costs less than $400, and requires minimal training.
A test with MiniDock, created by Guangzhou, China-based Pluslife Biotech, begins with collecting a tongue swab or phlegm sample. A machine spins and heats the tube containing the sample to release any genetic material. Then, a worker pours the sample into a slot on a test card and loads it into the MiniDock testing platform to detect TB bacterial DNA in 12 to 25 minutes.
Cattamanchi and colleagues collected tongue swabs and phlegm samples from 1,380 people aged 12 or older in seven countries with high rates of tuberculosis. MiniDock MTB successfully detected TB in 86 percent of TB-positive phlegm samples and 80 percent of TB-positive tongue swabs, meeting WHO accuracy targets. His tests with phlegm outperformed microscopic examination of smears by 24 percent and were similar to the standards for an expensive laboratory test.
But this inexpensive test has drawbacks. It was more accurate when detecting TB from phlegm compared to swabs. Cattamanchi notes that “accuracy isn’t everything” because for patients who can’t produce phlegm, a tongue swab is “the difference between getting a test and getting nothing.” Additionally, MiniDock MTB does not detect drug-resistant tuberculosisbut Pluslife is accelerate the development of such maps.
The sensitivity of the test decreased if the samples contained few bacteria, which occurs in the early stages of the disease. “It’s not just a problem for tongue samples,” says epidemiologist Emily MacLean of the University of Sydney, who was not involved in the study but is part of a group carrying out TB screenings with MiniDock. “When there aren’t a lot of bacteria present, it’s just harder for tests to find a signal.”
MiniDock should be used in conjunction with other tests to improve the chances of early detection of tuberculosis, says epidemiologist Amira Roess of the George Mason University College of Public Health in Fairfax, Virginia, who was not part of the study.
Cattamanchi and colleagues are also testing TB diagnostics based on RNA profiles found in blood, proteins and metabolites, to detect the disease without requiring any samples from the respiratory tract. Lingual swab tests can’t replace all tests, he says, but they can be a “tool to get the right test to the right person, at the right time.”
