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Type 1 diabetes screening: yay or nay?

Published on Nov 28, 2024

If you live with type 1 diabetes (T1D), do you wish you had known ahead of time? Would you have your children screened to find out their risk of developing this condition? Would you advise your friends and family to get screened?

These past few years, several research groups have found that the percentage risk of a person developing T1D can be predicted with a simple blood sample or fingertip swab, even if there are no apparent symptoms.

In Italy, T1D screening (sometimes with other autoimmune diseases, such as celiac disease) has been implemented for all children and youth aged between 1 and 17. 

In Canada, T1D screening is currently only available through research projects such as TrialNet, and is intended only for family members (parents, siblings, grandparents, etc.) of a person with T1D, who are 15 times more likely to develop the condition. However, 80–90% of people with T1D have no family history of the disease. So, screening relatives of people with T1D exclusively will miss 80% to 90% of new cases. Moreover, the CanScreen T1D consortium is running a pilot project to develop a screening program for the general population.

Should everyone get screened? Can our healthcare system handle such a task? 

What’s more, the question of whether or not to screen for T1D touches on several sensitive issues, including the right not to know, without having to provide any justification. Here’s some useful information to consider.

What is T1D screening?

Screening is not the same as a diagnosis. Screening gives information on the probability of developing the disease in a person who doesn’t have it, while diagnosis identifies the presence of the disease in a person with symptoms of T1D (intense thirst, frequent urination, weight loss). 

A positive screening result doesn’t necessarily mean that the person will develop the disease, but it indicates that the risk is relatively high. A positive diagnosis means that the disease is present and established.

Two types of screening

At this time, screening requires the collection of a blood or capillary sample (fingertip) to test for the presence or absence of one to four autoantibodies associated with T1D. These types of antibodies are markers in the blood that point to an attack on the insulin-producing cells of the pancreas. At the time of diagnosis, 95% of people with T1D have at least one of these autoantibodies. This analysis also differentiates between the different forms of diabetes (type 1, type 2 and LADA). 

When one of these antibodies is present in children, they have a 14% risk of developing T1D within 10 years; if two are present, the risk rises to 70%. However, autoantibodies may not be detectable at the time of testing and only become detectable at a later date. This is why screening tests must be repeated often to confirm earlier results.

Scientists generally consider that a person with at least two persistent autoantibodies will almost certainly develop type 1 diabetes, i.e. close to a 100% chance according to some studies. In Canada, T1D screening is currently only available in a research context.

Another type of screening, called polygenic risk score, is being developed. This test analyzes the genetic code (DNA) to find genetic variations associated with a predisposition to develop T1D or, on the contrary, with a reduced risk. The accumulation of hundreds of genetic variations combined give a final risk score, specific to the person tested, and stable over time.

As of now, this score has been validated mainly in people of European or Caucasian origin, but research is ongoing with other populations. As there are many determinants of T1D other than genetic, a high score doesn’t determine with certainty that a person will develop T1D.

Screening vocabulary

Antibodies: These proteins are like little soldiers created by your immune system to fight off external threats such as bacteria, viruses or toxins. 

Autoantibodies: These types of antibodies are soldiers that are misled by your immune system (autoimmune process); they mistake your own cells and tissues for external threats and attack them. These “rogue” soldiers are markers of the autoimmune disease.

Polygenic risk score: This score is just like a grade on a school report card, except it indicates the risk of developing a disease based on your genetic heritage (the information that is in your genes and their thousands of variations). And unlike a school grade, you don’t want this number to be high, as the higher it is, the higher the risk of developing a disease such as type 1 diabetes.

Is it good to know?

The main benefit of screening for T1D is to be able to detect the disease before it develops, which for monitoring the progression of the disease in order to avoid the risk of diabetic ketoacidosis (severe hyperglycemia with an accumulation of toxic substances called ketones), which requires hospitalization. Between 30% and 50% of people living with T1D are diagnosed following ketoacidosis. 

Also, a person who knows they’re at high risk of developing T1D can, with the support of healthcare professionals, prepare mentally and learn about the disease before the pancreas stops producing insulin. Conversely, it can be reassuring for someone who has a family member living with T1D to know that they don’t have the autoantibodies.

In the future, it will be possible to delay, and perhaps one day prevent, the onset of the disease. For example, in the United States, Teplizumab delays the onset of T1D by an average of two years. This treatment is the first in a promising new class of drugs. However, it’s not yet approved by Health Canada. Many other options are yet to come. 

Is it bad to know?

Of course, there are always two sides to every coin.

Finding out that you have a high probability of developing T1D can cause anxiety, excessive or unnecessary behaviours (e.g., no more sugar, no more travel) and stigma from those around you (e.g., exclusion, rejection, blame, devaluation), as well as make it more difficult to buy insurance (if you have to declare a positive screening test result to insurance companies).

Moreover, screening tests are not 100% accurate, so there is a risk of false positives (i.e., causing useless stress) or false negatives (i.e., causing a false sense of reassurance). This can be difficult to cope with mentally. Plus, having to repeat these tests when they are negative can become another source of anxiety. 

Blood tests can also reveal markers for other autoimmune diseases (if they are tested for), which can be a heavy burden.

Are you ready?

We need to think about the relevance, acceptability and feasibility of making screening available to the entire Canadian population. This assumes that the majority of people “want to know” and are prepared to live with the results. For example, in the event of a positive test, you may feel that you (or your child) are living with a sword of Damocles hanging over your head. It is therefore crucial to be properly educated about the risks and benefits of screening to be able to make an informed decision.

Is our healthcare system ready to support those who receive a positive result? As we all know, access to physical and mental health resources is already very difficult. What’s more, healthcare professionals are not yet trained to prescribe these tests, nor to follow up with patients.

The costs associated with these new tests could be invested in educating the population about diabetes symptoms (i.e., intense thirst, frequent urination, major fatigue, weight loss and recurrent infections), which would still allow time to get prepared, although not as much time. 

A number of research projects are currently underway to establish when and how to organize screening, and to support people who wish to do it.

What do you think? Are Canadians ready for T1D screening? The BETTER program would love to hear your opinion and that of your loved ones on the pros and cons of screening. Please fill out the following survey on type 1 diabetes screening, and don’t hesitate to pass it along!

 

References:

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Written by: Nathalie Kinnard, scientific writer and research assistant

Reviewed by:

  • Valérie Poulin, M.Sc. genetic counsellor, IRCM
  • Géraldine Gosse, M.Sc., CCGC, genetic counsellor, IRCM
  • Maha Lebbar, MD, Ph.D.
  • Rémi Rabasa-Lhoret, MD, Ph.D.
  • Anne-Sophie Brazeau, P.Dt., Ph.D.
  • Aude Bandini, Michel Dostie, Jacques Pelletier and Claude Laforest, patient partners of the BETTER project.

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