The diagnostic spinner in action.
Urinary tract infections have been called the “canary in the coal mine” of global antibiotic resistance. With more than half of all women having a UTI in their lifetime and men increasing in susceptibility as they age, UTIs are one of the most common bacterial infections in the world.
Because it’s not always possible to check for a bacterial infection in a urine sample, patients are often given antibiotics on the basis of symptoms alone—a practice that contributes to the growing resistance of many UTIs to the most common treatments.
We may be rescued by an unexpected hero: the fidget spinner. In a paper in Nature Biomedical Engineering this week, researchers in South Korea and India describe a new test for UTIs that needs nothing more than a couple of spins, by hand, of a spinner-like device. Its results—which can be read by anyone—are ready in around an hour.
Lab on a disc
Currently, UTIs are best diagnosed by urine culture tests, which are slow and resource-intensive. Dipstick tests—which just requires a treated paper strip to be dipped into a urine sample—are cheaper and available immediately, but they aren’t as reliable.
The ideal test would not only be fast and accurate but also as resource-light as a dipstick—useable in settings with no electricity, limited cash, and few trained professionals. That’s where the fidget spinner comes in.
A team of researchers led by Yoon-Kyoung Cho built a device that works on the same principles as a fidget spinner. Like the toy, it has small “wings” that spin around a central point; and like the toy, it can spin on its own for ages after just one or two nudges by hand. Unlike the three lobes of the common fidget spinner toy, this “lab on a disc” is rectangular. It makes up for that with much more interesting contents.
The testing device takes just 1ml of urine in a central chamber. When the device is spun, the centrifugal force pushes the sample through a membrane that catches any bacteria from the sample while the liquid filters through to a reservoir. When a dye is added, it filters through this sample of bacteria, changing color to indicate how high the bacterial load is. It takes less than an hour to get results visible to the naked eye.
Field testing
To road-test the device, the researchers took it to a clinic in Tiruchirappalli, India, where patients are usually given antibiotics based just on their symptoms. They collected samples from 39 UTI patients, and then tested them using conventional urine culture tests as well as the new device. The two methods had comparable results, although the spinner found a few extra patients who tested negative using conventional methods.
The team also used the device to test for antimicrobial resistance. They exposed bacterial samples in the test to different drugs and then compared them to samples that hadn’t been treated. The samples that stayed strongly colored by the dye were considered resistant. Although this wouldn’t rival gold-standard tests for microbial resistance, it could help doctors to make a quick decision about which antibiotic to prescribe.
One more test confirmed that the spinner could be used by anyone, regardless of hand size. The researchers checked spin speed differences between ten different test spinners, five men and five women. All of them could get the device to spin all of the urine sample through the filter, although some of them needed to give it more than one spin to do so.
Of those 39 patients in Tiruchirappalli, all would normally have been prescribed antibiotics based on their symptoms. Using the spinner, that number dropped to 18, which would save 21 people from getting an unnecessary prescription—and the risks, both personal and global, that come with it.
Nature Biomedical Engineering, 2020. DOI: 10.1038/s41551-020-0557-2 (About DOIs).