Microscopes cost money. Rats … not so much.

But each works equally well when it comes to determining whether a patient has tuberculosis. In fact, bacteria-sniffing rats may have the edge.

Tuberculosis, also known as TB, is not common in the United States, but it is a huge problem in developing countries.

The disease killed an estimated one-point-seven-million people in 2009 and nine-point-four million people developed TB last year, according to the World Health Organization.

TB is usually diagnosed by taking a sample of sputum … the unpleasant substance produced in the lungs and throat in people with respiratory infections … and staining it with dyes that stick to TB bacteria. Technicians look at the smear under a microscope to confirm TB.

The technique has been in use for a century, but can take up to three months to produce results.

Enter the rats.

Not ordinary rats, but Gambian pouched rats from Africa that weigh as much as 15 pounds.

Scientists rewarded the rats with banana for pausing at samples known to contain the TB germ, but not for pausing at other sputum samples.

In short order, the animals learned to pause only at samples that were positive for TB.

Rats detected the presence of tuberculosis as often as eighty-six percent of the time. Even higher was their sensitivity to the absence of the germ, which was over ninety-three percent.

The research, led by Western Michigan University scientists, suggests the technique needs refinement, but using rats to detect TB in the developing world is worth exploring.

But there are skeptics.

While some of the rats in the experiments became tuberculosis-detection experts, others … well, not so much.

But unquestionably the rats’ overall ability to detect TB as well as more traditional medical techniques is amazing.

And, in lieu of bananas, they work for peanuts.