Abstract
BackgroundDifferentiating between type 1 and type 2 diabetes is fundamental to ensuring appropriate management of patients, but can be challenging, especially when treating with insulin. The 2010 UK Practical Classification Guidelines for Diabetes were developed to help make the differentiation.AimTo assess diagnostic accuracy of the UK guidelines against ‘gold standard’ definitions of type 1 and type 2 diabetes based on measured C-peptide levels.Design and settingIn total, 601 adults with insulin-treated diabetes and diabetes duration ≥5 years were recruited in Devon, Northamptonshire, and Leicestershire.MethodBaseline information and home urine sample were collected. Urinary C-peptide creatinine ratio (UCPCR) measures endogenous insulin production. Gold standard type 1 diabetes was defined as continuous insulin treatment within 3 years of diagnosis and absolute insulin deficiency (UCPCR<0.2 nmol/mmol ≥5 years post-diagnosis); all others classed as having type 2 diabetes. Diagnostic performance of the clinical criteria was assessed and other criteria explored using receiver operating characteristic (ROC) curves.ResultsUK guidelines correctly classified 86% of participants. Most misclassifications occurred in patients classed as having type 1 diabetes who had significant endogenous insulin levels (57 out of 601; 9%); most in those diagnosed ≥35 years and treated with insulin from diagnosis, where 37 out of 66 (56%) were misclassified. Time to insulin and age at diagnosis performed best in predicting long-term endogenous insulin production (ROC AUC = 0.904 and 0.871); BMI was a less strong predictor of diabetes type (AUC = 0.824).ConclusionCurrent UK guidelines provide a pragmatic clinical approach to classification reflecting long-term endogenous insulin production; caution is needed in older patients commencing insulin from diagnosis, where misclassification rates are increased.
Highlights
Classifying patients with diabetes with type 1 or type 2 is fundamental to ensuring they receive correct management.[1,2,3] In clinical practice this can be challenging, with 7–15% patients misclassified in England, and large variations in practice.[4,5,6,7]Historical lack of clear clinical guidelines for diabetes classification is likely to have contributed to this variation
Most misclassifications occurred in patients classed as having type 1 diabetes who had significant endogenous insulin levels (57 out of 601; 9%); most in those diagnosed ≥35 years and treated with insulin from diagnosis, where 37 out of 66 (56%) were misclassified
Current UK guidelines provide a pragmatic clinical approach to classification reflecting longterm endogenous insulin production; caution is needed in older patients commencing insulin from diagnosis, where misclassification rates are increased
Summary
Classifying patients with diabetes with type 1 or type 2 is fundamental to ensuring they receive correct management.[1,2,3] In clinical practice this can be challenging, with 7–15% patients misclassified in England, and large variations in practice.[4,5,6,7]Historical lack of clear clinical guidelines for diabetes classification is likely to have contributed to this variation. International guidelines from the World Health Organization[8] and the American Diabetes Association[9] base classification on underlying aetiology, with type 1 described as a destruction of beta cells leading to absolute insulin deficiency These guidelines do not provide clear criteria or classification pathways for clinical use.[8,9] A pragmatic classification algorithm (Figure 1) was developed in 2010 by key diabetes stakeholders in the UK, and published by the Royal College of General Practitioners (RCGP) and (the previously existing) NHS Diabetes in their Coding, Classification and Diagnosis of Diabetes document.[4] This uses age at diagnosis and time to commencing insulin treatment from diagnosis as its diagnostic criteria. The 2010 UK Practical Classification Guidelines for Diabetes were developed to help make the differentiation
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