Preventing Misdiagnosis between Type 1 and Type 2

A program testing type 1 diabetes patients’ C-peptide levels found that approximately half of the group had a different form of diabetes.

In the United States, healthcare and prescriptions are among some of the costliest items for many people. What if we could find a way to help our fellow citizens with this cost and reduce misdiagnoses? Scotland is leading the world in finding these misdiagnoses among patients diagnosed with type 1 diabetes. They have started routinely testing these individuals to check their C-peptide levels. C-peptide is a byproduct of nat`ural insulin secretion. Therefore, in patients diagnosed with type 1 diabetes, there should theoretically be no C-peptide found, or very little; insulin used as a treatment for type 1 diabetes does not contain C-peptide. 

By testing the C-peptide levels, Scotland determines if patients diagnosed with type 1 diabetes have the disease. Other than the apparent type 1 and type 2 diabetes, other forms of diabetes are commonly misdiagnosed as these more common forms. With about one-third of all people with type 1 diabetes being involved in a misdiagnosis, ensuring they have the correct treatment course is crucial. Not only can this treatment change be life-changing, but also cost-effective. Patients will be on their way to more effective treatment, in addition to prevention of unnecessary hospitalizations or doctor visits. By providing access to the C-peptide level testing, Scotland prioritizes patient needs. This should always take place in healthcare but often falls short. 

Scotland began this program after they completed a trial run at a single medical center that provided enough backing to pursue a greater audience. In this trial run, over 800 patients were included. These patients had been previously diagnosed with type 1 diabetes for at least three years before the trial. Each patient was submitted to the C-peptide testing. 

A significant portion of the trial population, over 100 patients, were found to fall into an “intermediate” insulin secretion group. To be considered “intermediate,” the C-peptide level had to be over 200 pmol/L. This group was then further tested to determine why they produced so much insulin as “type 1” diabetes patients. The testing determined that approximately half of the group had a different form of diabetes. This group was diagnosed with either type 2 diabetes or monogenic diabetes. Greater than 40 patients were found to have type 2 diabetes, whereas over ten patients were found to have monogenic diabetes. The other half of intermediate insulin secreters were found to have more insulin secretion than what was theoretically determined. As insulin secretion is not black and white for the type 1 diabetes diagnosis, many patients can retain some form of beta-cell function for years after their initial diagnosis. This alone could be a factor in the cause of misdiagnosis of patients with diabetes. In addition to the insulin secreters, 1.5% of the original group were advised to discontinue insulin therapy, and 1.9% were found to have improved blood glucose after changing treatments. 

If the simple blood test of checking the C-peptide levels takes off, healthcare administrators and insurers may find substantial money saved by finding these misdiagnoses. This is because patients will save money by switching to appropriate therapy and will not be spending on healthcare for side effects associated with the wrong treatment. In addition, patients on correct therapy should likely experience long-term health benefits for their appropriately treated disease. The question is, when will this practice begin within the United States?

Practice Pearls:

• C-peptide is a byproduct of natural insulin secretion. Therefore, it is not found in medicinal insulin used in therapy for diabetes patients. 
• Benefits outweigh the risk when it comes to C-peptide testing. This simple blood test could save patients money in the long run. 
• Insurers and health administrators should be happy to consider this practice as it could provide a patient with long-term health benefits, prevent future hospitalizations and provide an opportunity for fewer doctor visits. 

“Roll-out of new diabetes test.” Press release, Government of Scotland. Oct. 30, 2021.

Foteinopoulou, M.W.J Strachan, et. al. “Impact of routine clinic measurement of serum C-peptide in people with a clinician-diagnosis of type 1 diabetes.” Diabetic Medicine, Nov. 1, 2020.

Wollen, Ross. “Why Scotland is Now Testing the C-Peptide Levels of Everyone with Type 1 Diabetes.” Diabetes Daily, 5 Nov. 2021.

Quinlynn Champ, PharmD Candidate 2022, South College School of Pharmacy