TB-sniffing rats get put to the test
In resource-poor developing nations, tuberculosis is typically diagnosed by analyzing a smear of a patient's sputum with a standard microscope – a method that's somewhat problematic. Now, scientists have confirmed that getting rats to sniff the samples is a better way to go.
The problems with the commonly-used smear tests are that the accuracy varies according to the quality of the sample, plus small children are often unable to provide enough sputum for analysis.
"As a result, many children with TB are not bacteriologically confirmed or even diagnosed, which then has major implications for their possible successful treatment," explains Dr. Georgies Mgode, of Tanzania's Sokoine University of Agriculture. "There is a need for new diagnostic tests to better detect TB in children, especially in low and middle-income countries."
Previously, African giant pouched rats (Cricetomys ansorgei) had been trained to indicate when they detected the scent of molecules released by tuberculosis-causing Mycobacterium tuberculosis bacterium in sputum. That project was inspired by anecdotal reports that people with the disease emitted a distinct odor.
Mgode's team recently got some of those rats to sniff sputum samples obtained from 982 children under the age of five. All of those samples had already been tested using the standard smear technique at clinics in the Tanzanian capital of Dar es Salaam. Those tests indicated that 34 of the children had TB. The rats, however, discovered an additional 23 cases of the disease, which were confirmed when the samples were analyzed using a more advanced light emitting diode fluorescence microscope.
"This intervention involving TB screening by trained rats and community based patient tracking of new TB patients missed by hospitals enables treatment initiation of up to 70 percent," says Mgode. "This is a significant proportion given that these additional patients were considered TB negative in hospitals, hence were initially left untreated."
A paper on the research was recently published in the journal Pediatric Research.