Evaluating the Practicalities & Potential Benefits of Using Remote C-peptide Testing in Clinical Practice to Confirm Established Type 1 Diabetes

Background It can be hard to diagnose type 1 diabetes in adults because the symptoms can overlap with type 2 diabetes and misclassification of type 2 and type 1 diabetes can occur. This matters as type 2 diabetes cases misclassified as having type 1 diabetes potentially receive a lifetime of unnecessary insulin treatment without access to the effective treatment strategies for type 2 diabetes. Whether someone needs treating as type 1 diabetes can be confirmed by measuring their insulin levels using a test called C-peptide. This should be measured when diabetes is longstanding (over 3 years diabetes duration) as, at diagnosis levels of insulin secretion can overlap in type 1 and type 2 diabetes. A study in Scotland measured C-peptide in a clinic of patients with long standing treatment as type 1 diabetes showing around 1 in 15 of cases did not have type 1 diabetes.

As a result, in Scotland all those with longstanding type 1 diabetes now have C-peptide measured and this is likely to be recommended across the UK. For newly diagnosed cases this will occur prospectively as part of patients' ongoing type 1 diabetes care. However, for existing cases, each hospital will need to test C-peptide, on a blood sample collected from a vein, in all patients in their type 1 diabetes clinic. In addition to the burden on clinical staff to collect the samples, this C-peptide test is not measured in many UK laboratories so co-ordinating this testing on all patients within a clinic will be extremely challenging.

We have recently validated a method of testing C-peptide on capillary blood (finger prick) samples. Importantly these can be collected by a patient at their home and can be posted back to any UK laboratory where C-peptide measurement is available. Using this approach means that clinic visits for blood collection are not required and testing can be co-ordinated from a central location, making organising testing in a whole clinic much more straightforward.

Study Aims & Participation The aim of this research is to assess the practicalities & potential benefits of collecting home finger prick samples from all patients within a hospital type 1 diabetes service to test how much insulin each patient is producing. To do this we will send detailed study information, sample collection kits and reply-paid return packs to 1500 randomly selected patients from a type 1 diabetes clinic (3000 patients in the whole clinic). We will ask participants to consent to take part (either online or by completing a paper consent form returned with their pack) before collecting a finger prick blood sample. We will ask participants to collect the sample between 1 and 5 hours after a meal and to check and record their blood glucose level at the same time. Participants would then return the sample and glucose result, using the pre-paid pack provided to the hospital clinic laboratory for a test called C-peptide (a measure of how much of their own insulin a person is producing). The sample collection process should take no longer than 10 minutes.

We will record the percentage of patients returning samples within 4 weeks of initial contact and determine the number of cases with high C-peptide suggestive of non-type 1 diabetes. If this study shows remote C-peptide testing is practical, and acceptable to patients, it could lead to remote testing being offered at all type 1 diabetes clinics in every hospital in the United Kingdom. Diabetes UK estimates around 350,000 people in the United Kingdom have type 1 diabetes. Reclassifying 1 in 15 people would mean approximately 23,000 people nationally could benefit from being identified as potentially able to stop insulin treatment.