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New method may have left thousands of diabetics without a diagnosis

For decades, the number of people diagnosed with type 2 diabetes has steadily increased – until 2012 when this trend suddenly stopped. Danish researchers now link this development to the roll-out of a new diagnosis method.

Each year thousands of Danes are not being diagnosed with type 2 diabetes since the launch of a new method in 2011, says PhD. at Aarhus University Jakob Schöllhammer Knudsen. Photo: Aarhus Universitet

The launch of a new method for diagnosing type 2 diabetes may have resulted in thousands of Danish diabetics and millions of people worldwide being left without diagnosis and treatment.

This is the conclusion of a new Danish study, which has examined a striking change in the number of people who are newly-diagnosed or treated for the first time for type 2 diabetes each year.

The researchers actually chanced upon the strange development which they then set out to study more closely.

"We wanted to study how the risk of dying has changed for newly-diagnosed diabetes patients over the years, and in doing so, we discovered that something very strange happened around the year 2012. So we then decided to take a closer look into this," says Jakob Schöllhammer Knudsen, who is a medical doctor and PhD At Aarhus University and the principal author of the study.

Sudden increase

He refers to the statistics showing that the number of persons either newly-diagnosed or treated for the first time for type 2 diabetes rose steadily from 1995 to 2012 and doubled from 193 to 396 per 100,000 inhabitants during this period. Then this trend suddenly changed, and until 2018 the number of diagnoses fell by 36 per cent.

A decrease in the number of people with diabetes diagnoses might initially sound like a good and healthy development. However, it is doubtful that the figures show that fewer people actually developed diabetes.

According to the researcher, the more obvious explanation is that the practice used for diagnosis has been altered.

"We discovered a very striking correlation with the introduction of a new way of diagnosing persons with diabetes in 2012, which was intended to provide an alternative to the two methods that were already in use," he explains.

New de facto norm

At the end of 2011, the World Health Organisation began to recommend using a fixed limit on long-term blood sugar level (HbA1c) to diagnose type 2 diabetes, making it possible to make a diagnosis on the basis of a simple blood test and meaning there was no need for a fasting blood sugar test or a glucose tolerance test.

Even though the new method was never intended to replace the other two, this is nevertheless what has happened in practice. And it may have shifted the entire epidemiology around type 2 diabetes.

"The three methods identify different types of patients, but the new method is easier to use and less stressful for both doctors and patients. Our study shows that doctors have to a high degree stopped using the other two methods in the course of a short period of time, and thus the HbA1c method became the de facto norm for diagnosing type 2 diabetes. And because HbA1c is less sensitive than the other methods, it also identifies fewer patients," explains Jakob Schöllhammer Knudsen.

In his assessment, between 3000 and 5000 Danes who would previously have been diagnosed with type 2 diabetes annually will no longer be diagnosed due to the new practice, which has also been rolled out over most of the world.

Rise in mortality rate

While the number of diagnoses has fallen since 2012, the opposite has happened for the mortality rate among newly-diagnosed type 2 diabetics.

Between 1995-2012, the mortality rate among type 2 diabetic patients fell by 44 per cent. Before it subsequently rose by 27 per cent to 48 per 100,000 inhabitants.

Much of this development can probably also be explained by the launch of the new method, as it no longer identifies patients with mild forms of diabetes below the HbA1c threshold.

But what are the consequences of thousands of Danes and millions of people worldwide being left without diagnosis and treatment?

Risks of further worsening

According to Jakob Schöllhammer Knudsen, it is too early to say anything about this.

"Basically, we can't say because we don't know who hasn’t been diagnosed and whether they might have been diagnosed anyway with some delay. We haven’t looked into who didn’t receive first-time treatment or hospital diagnosis, so we don’t know how they are getting on. But if we had tested for type 2 diabetes using the other methods, then we must assume that they would have been diagnosed and treated to the same extent as the others," he says and continues:

"However, I think it’s reasonable to assume that it will increase the risk of further worsening and complications for those patients who aren’t diagnosed with diabetes in time. We’ve carried out another study that shows that people just below the HbA1c threshold for diabetes actually have a higher risk of serious complications than those that are just above the diabetes threshold. Presumably because receiving a diabetes diagnosis leads to beneficial lifestyle changes and preventative treatment.”

Denmark is not the only country that has registered a significant decrease in the number of newly-diagnosed type 2 diabetics.

Experts in the area have previously pointed to the new diagnostic tool, but the lack of population-based HbA1c data stretching over a number of years has so far prevented researchers from examining developments in more detail.

The new study from the Department of Clinical Epidemiology at Aarhus University Hospital and  Aarhus University is based on data from 415,553 persons with type 2 diabetes.

The research result - more information

  • Type of study Observational register based study
  • Partners: Aarhus University, Aarhus University Hospital, Danish Diabetes Academy, Odense, Steno Diabetes Center, Aarhus, School of Public Health, Imperial College London. 
  • Financed by: Aarhus University. 
  • Conflict of interest: None
  • Published: In The Lancet Regional Health Europe January 1. 2022. 


Further information 

Jakob Schöllhammer Knudsen, MD, PhD. at Aarhus University. 

Phone: +4540540220

Mail: jsk@clin.au.dk