Type 1 diabetes (T1D) is a chronic condition, affecting 1 in 490 children under the age of 15 years. It is caused by the immune system damaging the pancreas, the organ which makes insulin. T1D has recognised stages before symptoms develop, providing an opportunity for early diagnosis, education and treatment which may delay the onset of symptoms.

Type 2 diabetes (T2D) is also a chronic condition where the body cannot make enough insulin, or cannot respond to the insulin properly. It is usually related to obesity, rather than an immune problem. It is more common in adults, but the early stages often start in childhood (up to 1 in 4 children in some clinics). Like T1D, early detection can delay onset of T2D, or even prevent it altogether.

Early diagnosis of T1D or T2D often relies on a test called the oral glucose tolerance test (OGTT), which is commonly used but not well tolerated, possibly because it requires a drip inserted into the vein, and several blood samples taken over 2-3 hours in a healthcare setting.

Our study aims to test whether we can do an OGTT using a finger-prick to test glucose, at home. We call this the 'GTT@home'. The finger-prick creates a drop of blood, which is done before and two hours after drinking a sugary drink. We will also explore whether a continuous glucose monitor (CGM), which reads glucose levels through the skin could be an alternative. We plan to recruit 90 children and young people, across two groups to assess the GTT@home.

To understand the experiences of those involved in monitoring, we will invite young people, parents and healthcare workers to take part in an interview, to understand the impact of testing to predict clinical T1D.

Group 1 will assess the accuracy of measuring glucose from a finger-prick blood test when compared to a blood test from the vein. We will recruit individuals who are having an OGTT as part of a research study, for clinical care or if they have agreed to have an OGTT for this study. Those with T1D will be invited to wear a CGM to explore its use as an additional, practical alternative.

Groups 2 and 3 will assess how well the GTT@home test works when done at home and how acceptable it is. This will only be offered to those known to be at risk of T1D.

These studies will help us to understand if the GTT@home can be used in routine care.

Inclusion criteria:

Cohort 1

• Willing and able to give informed consent for participation, or assent with parental consent
• Aged < 18 years old
• Able to consume oral glucose drink within 10 minutes
• Undergoing an OGTT, or consent to have one

Cohort 2

• Positive for two or more islet autoantibodies at any time
• Willing and able to give informed consent for participation, or assent with parental consent
• Aged < 18 years old
• Able to consume oral glucose drink within 10 minutes

CGM sub-study

• Willing and able to give informed consent for participation, or assent with parental consent
• Aged < 18 years old
• Able to consume oral glucose drink within 10 minutes
• Confirmed to have stage 1, 2 or 3 T1D
• Participation in Cohort 1

Qualitative sub-study

• Willing and able to give informed consent for participation, or assent with parental consent Then EITHER
• A young person positive for two or more islet autoantibodies (15 years old and above) at any time, or parent of a young person who has experienced a metabolic test e.g. OGTT OR
• A healthcare professional involved in delivering metabolic testing

Cohort 3

• Prediabetes diagnosis as above
• Willing and able to give informed consent for participation, or assent with parental consent
• Aged < 18 years old
• Able to consume oral glucose drink within 10 minutes

Exclusion Criteria:

Cohort 1

• Any known haemoglobinopathy
• Cystic fibrosis related diabetes
• Non-English speaker

Cohort 2

• Any known haemoglobinopathy
• Known clinical diabetes and on treatment
• Non-English speaker
• No recent weight available (within 3 months of study visit) and unable to obtain new weight measurement

CGM sub-study

• Any known haemoglobinopathy
• Cystic fibrosis related diabetes
• Non-English speaker
• Any active skin issue which would prevent the use of a CGM device

Qualitative sub-study

• Non-English speaker

Cohort 3

• Known clinical diabetes and on treatment
• Non-English speaker
• No recent weight available (within 3 months of study visit) and unable to obtain new weight measurement

Cohort 1 - Children < 18 years of age. To get a spread of glucose values, we will aim to recruit approximately equal numbers of participants with normoglycaemia, dysglycaemia and hyperglycaemia.

Cohort 1 CGM sub-study - Children < 18 years of age, who have T1D stage 1, 2 or 3 and undergoing an OGTT in cohort 1.This sub-study will be additional and optional to cohort 1.

Cohort 2 - Children < 18 years of age, who are identified as having stage 1, 2 or 3 T1D will be invited to take part in an OGTT at home.

Cohort 3 - Children < 18 years of age, who are identified as having pre-T2D.

Qualitative sub-study - Young people ≥ 15 years old with T1D stage 1, 2 or recent stage 3 (up to 12 months), who have been involved in metabolic follow-up, will be invited to take part. Parents of a child (of any age) with T1D stage 1, 2 or recent stage 3 will also be invited. Healthcare professionals involved in delivering metabolic follow-up for children with diabetes antibodies will also be invited.

Dates of birth will not be shared, but ages (possibly grouped) will be provided.

IPD and supporting information will be availabile once the primary paper for the study has been published.

Subject to participant consent, data will be shared with other researchers for research projects that have appropriate ethical approval. Requests for access to the data will be controlled by the Data Access Committee.