Many cases of Type 1 diabetes diagnosed after the age of 30 are being misdiagnosed as Type 2, leading to delays in receiving appropriate treatment, research has suggested.
Scientists at the University of Exeter said Prime Minister Theresa May is a high-profile example of someone who was initially diagnosed with Type 2 diabetes, only to later return to her doctors when her treatment did not work and find she had Type 1.
Type 1 diabetes is characterised by the rapid and severe loss of insulin production due to the cells in the pancreas which produce the hormone being attacked and destroyed by the body’s own immune system.
Individuals with the disease lose the ability to make their own insulin and therefore require regular doses of insulin to control their blood glucose, either in the form of injections or via a pump, and, unlike many people with Type 2 diabetes, cannot manage their condition through diet, exercise and blood sugar monitoring alone.
Type 2 diabetes is more common than Type 1, with around 90% of all adults with diabetes in the UK having Type 2.
For their study, researchers characterised Type 1 diabetes as being the rapid onset of insulin dependence within three years of initial diagnosis, together with a severe deficiency of insulin production by the pancreas.
They analysed a population cohort of 583 individuals who had insulin-treated diabetes that had been diagnosed after the age of 30.
The characteristics of their disease were compared with other participants who still produced some insulin, as well as with 220 individuals with severe insulin deficiency that was diagnosed before the age of 30.
The study found that 21% of those with insulin-treated diabetes who were diagnosed after the age of 30 had severe insulin deficiency, confirming Type 1.
Out of this group, 39% did not receive insulin when they were initially diagnosed, with 46% of those individuals self-reporting that they had Type 2 diabetes.
A rapid progression to insulin dependence was highly predictive of late-onset Type 1 diabetes, with 84% of those with the disease requiring insulin within just one year.
Among participants who became insulin-dependent within three years, 44% developed a severe deficiency of their body’s own insulin.
Their clinical, biochemical, and genetic characteristics were found to be comparable to those of participants who had been diagnosed before the age of 30.
In contrast, patients who retained some insulin production had substantially lower Type 1 genetic risk scores, antibody positivity (linked to the immune response that damages pancreatic cells), and a higher body mass index (BMI).
Where insulin treatment had been delayed, the patients were found to be on average older (48 years versus 41 years for those who received insulin immediately), and only 50% had self-reported as having Type 1 diabetes, compared with 96% of individuals who had been given insulin upon initial diagnosis.
These patients were also much more likely (29% versus 7%) to have been given oral hypoglycaemic drugs in an attempt to control their disease.
The research is being presented at the annual meeting of the European Association for the Study of Diabetes (EASD) in Berlin.
Dr Nick Thomas said: “Type 1 diabetes leading to severe insulin deficiency has similar clinical and biological characteristics to that occurring at younger ages, but is frequently not identified.
“Clinicians should be aware that the majority of patients needing insulin within three years of diagnosis will have Type 1 diabetes, even if they were initially thought to have Type 2 diabetes and did not need insulin at diagnosis.
“Getting the right diagnosis is important for these patients to receive the right education and treatment.”
Lucy Trelfa, of the charity Diabetes UK, said: “Diabetes is a very complex condition, with many different types, and as such can sometimes be difficult to diagnose.
“Getting the right diagnosis of diabetes is essential as Type 1 and Type 2 diabetes have very different treatment strategies.
“There’s still more we need to understand about the real life implications of misdiagnosis, but this research reminds us once again that people can develop Type 1 diabetes at any age.
“It’s therefore essential that healthcare professionals don’t rule out Type 1 in adults presenting with diabetes, and consider specialist referral where necessary, to help them make what can often be a tricky diagnosis.”