Northwestern Medicine doctor's discovery at Glenview clinic leads to labeling change for medicine
Dr. Emily Szmuilowicz, an endocrinologist, had been seeing her 72-year-old diabetes patient Wendy Seibel at the Glenview Outpatient Center for years, but during a routine appointment, Wendy informed her that every time she took her hydroxyurea, a medication used to treat certain blood disorders, the readings on her continuous glucose monitor would spike dramatically.
The glucose readings would stay that way for about 6 hours and then it would eventually come down. Though her CGM readings would be high, if she did a traditional finger stick glucose measurement, it was much lower. They were not consistent.
Wendy explained that she would try to switch up the times she took her medication to see if that made a difference. But, still, the readings said there was a spike in her sugar levels. She even called Dexcom, the maker of her CGM, to let them know what she was seeing, but hydroxyurea wasn't on the list of medications that could potentially spike her sugar levels.
When Wendy explained this to Dr. Szmuilowicz, and since this had not been previously reported, Dr. Szmuilowicz decided to do some testing to confirm what her patient had observed.
She had Wendy fast, then take her medication, and then compare the CGM reading to her finger stick glucose level every hour. Each time, the CGM showed a spike, even when she had nothing to eat. They did this at different times of the day, after different meals, and it always showed a spike in her CGM glucose level, even though the finger stick level did not spike.
These results confirmed to Dr. Szmuilowicz that hydroxyurea was, in fact, likely interfering with the CGM readings.
"If my level was typically around 80, the CGM would show 180," Wendy said. "If I were on a pump and didn't know my readings were wrong and it automatically increased my insulin level, it could have caused me a lot of harm."
Dr. Szmuilowicz discussed it with her colleague, Dr. Aleppo, and they reached out to the CGM manufacturer about their findings. The company performed testing on their own and was able to confirm that hydroxyurea, in fact, was interfering with her glucose levels. This led to an official FDA label change.
Wendy also wore two different glucose monitors simultaneously for two weeks, which showed divergent results and confirmed the interference, and these findings were recently published in the Diabetes Care.
"It makes me really proud to see how a novel discovery and contribution has come out of our very own Glenview diabetes program," said Dr. Szmuilowicz. "And that, at the heart of the discovery, was just listening to the patient. I think it says a lot about how we approach our patient care."
"The credit goes to Dr. Szmuilowicz," said Wendy. "When I first called the company, they just said it can't be, even though I was convinced that it was happening. Dr. Szmuilowicz took the time to listen to me, was able to confirm my findings, and worked hard to get this officially entered as medication that could affect blood sugar levels. She could have easily just told me that isn't possible, as it wasn't on the original list. I'm relieved that my findings were confirmed, so it couldn't potentially cause harm to anyone else."
"This really showcases the academic-community partnership that exists here," said Micah Eimer, MD, cardiologist and medical director at the Glenview Outpatient Center.
"This also serves as a good reminder to always listen to the patient, no matter what the circumstances present. I'm incredibly proud that my colleague worked to make sure there was additional testing on this issue, and saw it through until there was an official FDA label change."
Wendy mentioned that her daughter, who also has Type 1 diabetes, recently forwarded her an email she received from the maker of her CGM, informing her that hydroxyurea is a medication that can spike glucose levels. She knew she received this warning because of her mom, who was determined to make a difference.