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Curious Brief Report
Do I Smell a Rat Smelling TB?
By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases. Dr. Kemper does research for Abbott Laboratories and Merck. This article originally appeared in the February issue of Infectious Disease Alert. At that time it was peer reviewed by Timothy Jenkins, MD, Assistant Professor of Medicine, University of Colorado, Denver Health Medical Center. Dr. Jenkins reports no financial relationship to this field of study.
Source: Poling A, et al. Using giant African pouched rats to detect tuberculosis in human sputum samples: 2009 findings. Am J Trop Med Hyg 2010;83:1308-1310.
As reported in 2003, the world bank began funding a project to train giant pouched Gambian rats to sniff out tuberculosis (TB) in sputum specimens in sub-Saharan Africa. Rats have been successfully trained to target landmines, and using a similar training/reward technique, pilot data suggested that rats could be trained to detect TB in respiratory specimens. Compared to a trained technician (~ 95% accuracy), preliminary data in 2003 suggested the rats were able to detect TB in 92% of smear-positive cases and 77% of culture-positive cases, with a 2% false-positive rate.
The rats have since gotten better. Although trained technicians were able to identify AFB in 13.3% of 10,523 respiratory specimens by light microscopy, the rats were able to detect an additional 600 cases. When multiple rats were allowed to pause for 5 seconds over each specimen, the specificity improved to 89%. All it takes is training and bananas. Compared to a trained technician, who can process about 20 specimens in a day, the rats are much more efficient but they don't do any clean up.