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A way to empower kidney patients to monitor their blood potassium levels

19 October 2021

At Kidney Research UK, we are determined to push research beyond the discovery stage to the point where it can make a difference to kidney patients’ lives. We caught up with Professor Fiona Karet, professor of nephrology at the University of Cambridge, honorary consultant at Addenbrooke’s Hospital, and former Kidney Research UK trustee, whose work is nearing implementation. With help from our funding, Fiona and her team are developing a hand-held device to quickly and simply measure potassium levels to empower kidney patients to monitor their own potassium.

Fiona Karet
Fiona Karet in the lab

Why are potassium levels important?

Potassium plays a crucial role in the body — it helps to balance blood pressure and supports nerves and muscles. In healthy individuals, the kidneys control potassium levels. But if the kidneys are not working properly, levels of potassium in the body can become dangerously high, or in some patients low, and this can be fatal. Low potassium causes symptoms such as fatigue, weakness, cramps or seizures, but if potassium levels get too high, people generally have no symptoms until it is too late.

There is currently no way for kidney patients to measure their own potassium levels — they can only be measured via a blood test at the hospital or GP surgery. This is time-consuming, costly, and can give inaccurate readings if there is a delay between taking the sample and carrying out the analysis. This means that often patients must take precautions that affect their quality of life, such as eating a low potassium diet, without knowing whether they are necessary.

Transforming potassium monitoring

In her clinic, Fiona saw many patients suffering due to potassium imbalances, with no means of managing their condition themselves. From what they told her, she realised that this was a huge unmet clinical need and had the idea to produce a hand-held device for measuring potassium. A simple finger-prick test, much like diabetic patients use to measure their blood glucose, would allow patients to monitor their potassium levels instantly and adjust their diet and medication accordingly.

As well as enabling patients to monitor their potassium at home, the device would be valuable in many situations.

“GPs, cardiologists and dialysis units could use the device for immediate results. It could also be used to plan medication schedules, so patients only take medications in the time windows where they absolutely need them,” Fiona explained.

Developing the device

With our funding, Fiona and her team set about developing the sensor. “We were awarded two Kidney Research UK grants, which enabled us to progress to the point where we needed a lot more investment,” Fiona explained. To further develop and manufacture the device, and with our help, the team set up a spin-out company – Kalium Health.

The device includes single-use test strips which measure potassium from a drop of blood in only one minute. “Blood is drawn through a small tube into the test strip which has a potassium-sensitive chemical on an electrode system.” Fiona explains. “This generates an electrical signal which gives a readout telling you the potassium level in the blood.”

Although the concept is simple, development of the sensing technology has been far from straightforward and has required a truly multidisciplinary approach. “We’ve got chemists, physicists, engineers and clinicians working on this,” Fiona explained.

The team have made fantastic progress but there are more steps — which Fiona predicts could take another two to three years— before this device reaches patients.

They are beginning to test their prototype devices with human blood samples from healthy volunteers, which will be followed by samples from patients. These initial studies are checking that the blood sampling method is robust and that the device gives accurate enough and reproducible results. Then the next steps will be to test the device in clinical trials to get regulatory approval for patient use.

Patients at the heart of the research

Although the work is hard, Fiona and the team remain driven by kidney patients, who are vocal about how this device will change their lives.

Patients involved in developing this research said:

“Being able to measure my potassium level would make a huge difference to my life because it would put me in the driving seat.”

“This would literally change my life. I could plan my day, schedule infusions, adjust supplements and medications at the first sign of change on the meter instead of after I crash.”

Fiona has been a loyal supporter of ours for many years, ever since she began her impressive academic career with one of our training fellowship awards, and she remains deeply appreciative of the support from the charity.

“This project would never have started without Kidney Research UK’s funding. It was a leap of faith for the charity, and I and my team are hopeful it will be well repaid!” she says.

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