Simple, cheap C-Peptide helps patients get the right diabetes diagnosis and treatment

Researchers at the University of Exeter Medical School have developed simple and inexpensive ways to measure C-peptide and have demonstrated that this test can show what treatment will be most effective for people with diabetes. Clinicians at the Western General Hospital in Edinburgh have used the new test on every person thought to have type 1 diabetes for over three years in their clinic and shown that some actually have other types of diabetes and can stop insulin treatment.

C-peptide is produced at the same time and in the same quantities as the insulin that regulates our blood sugar. By measuring C-peptide levels, doctors can now tell how much insulin a person is producing themselves, even if they are taking insulin injections as treatment.

The Exeter team has developed a new urine test for C-peptide, and shown that a simple blood test when a person is seen in clinic can also accurately measure C-peptide, replacing previous methods which were expensive and time-consuming. These tests are now available in nearly every hospital in the UK, and cost as little as £10.

The team demonstrated how urine and blood C-peptide can be used to robustly identify what type of diabetes a person has, and help identify what treatment will work for them. This is crucial to getting the right treatment, education and follow-up care. By offering this test to people thought to have Type 1 diabetes in their clinic, the Edinburgh researchers have shown that many have high C-peptide, raising the possibility of other types of diabetes. Some of these patients have been able to stop insulin and switch to tablet treatment. This testing also revealed that in some of these patients, the diabetes had a genetic cause, which is important both for treatment and for other people in their families.

Professor Mark Strachan, from Western General Hospital, Edinburgh, said: “We have now measured C-peptide in over 750 people with a clinician-diagnosis of Type 1 diabetes, attending our clinic at the Westen General Hospital. So far, we have made a new diagnosis of genetic diabetes in eight people, and changed the diagnosis to Type 2 diabetes in 28 other people. This has allowed us to make changes to treatment in many of these individuals and in 12 people we have actually been able to stop insulin therapy.”

The team’s research also shows that C peptide testing is practical in clinics. They identified optimal storage conditions for the samples, which were previously thought to be unstable, so sample collection is now much easier. They showed that using a specific preservative means that blood C-peptide is stable for more than 24 hours. For the first time, this means it is viable to conduct a test to be measured in primary care and outpatient clinics. This evidence together removed crucial barriers to implementation that had previously blocked widespread adoption of this test in routine clinical care.

University of Exeter

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