The diagnosis of a child with type 1 diabetes is usually straightforward. The symptoms are classic and well-known to any physician—polydipsia, polyphagia, and polyuria: the child with uncontrolled blood sugars is forever thirsty, hungry and running to the bathroom to urinate.
But the misdiagnosis of type 2 in an older patient who really has type 1 or LADA (latent autoimmune diabetes) is becoming more common. It is something that is seen on a regular basis at the Joslin Diabetes Center. Patients will come into the clinic because they haven’t been able to get their blood glucose under control despite their best efforts with diet and exercise. They often don’t feel well and some have continued to have inadequate blood glucose control since diagnosis.
Diagnosis of the middle-aged adult with type 1 diabetes isn’t always dramatically obvious. Type 1 diabetes in adults in their 30s and beyond doesn’t always follow the same pattern of symptoms as when it presents in children and teenagers.
Instead of the severe illness that usually accompanies the diagnosis of a child with type 1, people may experience mild symptoms such as fatigue, vision problems or gradual weight loss without a change in appetite or intake. Elevated glucose levels may be found on routine physical exam.
Often physicians can identify someone with type 1 diabetes because they have low levels in the blood of C-peptide, which is part of the precursor protein that eventually becomes functional insulin. When the beta cells secrete insulin they also release the C-peptide into the blood, so checking C-peptide levels is one of the ways to distinguish those with beta cell failure
But laboratory tests aren’t always useful. “Unfortunately, C-peptide isn’t very helpful in distinguishing type 1 in ‘older’ adults,” says Aaron M. Cypess, MD, PhD, Assistant Investigator and Staff Physician at Joslin. “Beta cell destruction is a slow process in these patients,” says Cypess, “and the normal response to high glucose levels in people with functioning beta cells is a rise in C-peptide.” So the beta cells that remain pump out as much C-peptides and insulin as they can, making the test results seem normal.
If a primary care physician who isn’t an expert in diabetes draws a C-peptide on a patient with gradually developing type 1 the results might lead him to conclude the patient had type 2.
Levels of autoantibodies to insulin and the beta cells can be of some value but even these do not lead to an air-tight diagnosis. This is because not all people with type 1 have these antibodies.
So the diagnosis is still largely a clinical one. “I am always suspicious when someone who is thin and has no family history is classified as type 2,” said Dr. Cypess. “My suspicion increases if she/he has rapidly gone through a series of oral meds without success, especially if she/he has been following a healthy lifestyle.”
Like all type 1’s, these patients will eventually need insulin. Still, many can be controlled on oral agents for quite some time. If their A1c is still in the target range, orals coupled with diet and physical activity can be continued. Others who present with an A1C in the 9’s or above are probably going straight to insulin, although they may continue with oral agents in addition to insulin as there is some evidence that maintaining beta cell mass with the use of orals or other drugs can extend the period until complete beta cell failure for up to three years.
If you’re a patient who has been diagnosed with type 2 but have the following symptoms you may want to discuss it with your health care provider or go for a second opinion.
- You have always been thin
- You have no family history of diabetes
- You have rapidly progressed from one oral drug to two or three with limited improvement or degradation in your glucose control
- You exercise regularly and have been following a healthy carbohydrate modified diet and this has not helped
You can read about patients’ experiences with this type of diagnosis mix-up in this piece from the Wall Street Journal