It’s now possible to use a USB stick to measure the levels of HIV in a patient’s blood. The device has a 95 percent accuracy rate and takes less than 30 minutes, which is a big improvement over current tests.

Patients usually need to send fluids to a lab to test their HIV levels. Depending on the specific test, it can take days or weeks to get results. In a study published this week in Scientific Reports, researchers from both Imperial College London and tech company DNA Electronics created a tiny device that does the same thing.

It works like this: you put a drop of blood on the USB stick. This changes the acidity levels of the metal in the USB. A chip inside the USB notes the change in acidity and turns this into an electrical signal. It can then be connected to a computer or other hand-held device, where the researcher can read out the result. The scientists tested 991 blood samples. They received the results in an average of 21 minutes.

This technology probably won’t make it to market soon, but it could lead to a big improvements when it does. The USB is easy-to-use and disposable, which means that it can be used to administer HIV tests in more rural or inaccessible areas. And because the process is pretty simple, patients can learn to monitor their own levels of HIV to make sure their medication is working.