Can clinical features be used to differentiate type 1 from type 2 diabetes? A systematic review of the literature

Abstract

ObjectiveClinicians predominantly use clinical features to differentiate type 1 from type 2 diabetes yet there are no evidence-based clinical criteria to aid classification of patients. Misclassification of diabetes is widespread (7–15% of cases), resulting in patients receiving inappropriate treatment. We sought to identify which clinical criteria could be used to discriminate type 1 and type 2 diabetes.DesignSystematic review of all diagnostic accuracy studies published since 1979 using clinical criteria to predict insulin deficiency (measured by C-peptide).Data sources14 databases including: MEDLINE, MEDLINE in Process and EMBASE. The search strategy took the form of: (terms for diabetes) AND (terms for C-Peptide).Eligibility criteriaDiagnostic accuracy studies of any routinely available clinical predictors against a reference standard of insulin deficiency defined by cut-offs of C-peptide concentrations. No restrictions on race, age, language or country of origin.Results10 917 abstracts were screened, and 231 full texts reviewed. 11 studies met inclusion criteria, but varied by age, race, year and proportion of participants who were C-peptide negative. Age at diagnosis was the most discriminatory feature in 7/9 studies where it was assessed, with optimal cut-offs (>70% mean sensitivity and specificity) across studies being <30 years or <40 years. Use of/time to insulin treatment and body mass index (BMI) were also discriminatory. When combining features, BMI added little over age at diagnosis and/or time to insulin (<1% improvement in classification).ConclusionsDespite finding only 11 studies, and considerable heterogeneity between studies, age at diagnosis and time to insulin were consistently the most discriminatory criteria. BMI, despite being widely used in clinical practice, adds little to these two criteria. The criteria identified are similar to the Royal College of General Practitioners National Health Service (RCGP/NHS) Diabetes classification guidelines, which use age at diagnosis <35 years and time to insulin <6 m. Until further studies are carried out, these guidelines represent a suitable classification scheme.Systematic review registrationPROSPERO reference CRD42012001736.

Men across a range of ethnicities have a higher prevalence of diabetes: findings from a cross‐sectional study of 500 000 UK Biobank participants

“…We attempted to ensure the majority with Type 1 diabetes were not included in the sensitivity analysis by excluding those with an age at diagnosis of diabetes of ≤ 30 years . However, we acknowledge that this exclusion may misclassify some.…”

“…Because of differences in characteristics within the South Asian population, a subgroup analysis was also performed. Finally, sensitivity analysis was performed excluding individuals with probable Type 1 diabetes by removing those diagnosed with diabetes aged ≤ 30 years .…”

Definition, Classification and Diagnosis of Diabetes, Prediabetes and Metabolic Syndrome

“…acanthosis nigricans) are more common in children and adolescents with type 2 diabetes than type 1 diabetes. In adults, a systematic review of clinical indicators identified age at diagnosis of diabetes <30 to 40 years, and time to needing insulin <1 to 2 years as more predictive of type 1 diabetes than body mass index (BMI) (4).…”

The Role of Laboratory Testing in Differentiating Type 1 Diabetes from Type 2 Diabetes in Patients Undergoing Bariatric Surgery

“…Thus, there is advocacy to perform bariatric surgery in patients with type 2 diabetes at body mass index (BMI) as low as 30 kg/m 2 [2], and prospective studies have begun to evaluate patients with even lower BMI [3]. Performing bariatric surgery in patients at a lower BMI increases the likelihood that surgical candidates may include patients with type 1 diabetes who have been misdiagnosed as having type 2 diabetes [4]. …”