Laboratory Tests for Type 1 Diabetes Diagnosis and Management
For type 1 diabetes diagnosis and management, the recommended laboratory tests include HbA1c, fasting plasma glucose, autoantibody testing, and urine albumin-to-creatinine ratio measurements, with HbA1c being measured every 3 months until targets are reached and then at least every 6 months thereafter. 1, 2
Diagnostic Laboratory Tests
- Plasma glucose rather than HbA1c should be used for diagnosing the acute onset of type 1 diabetes in individuals with symptoms of hyperglycemia 3
- Diagnostic criteria include:
- Standardized islet autoantibody tests are recommended for classification of diabetes in adults when there is phenotypic overlap between type 1 and type 2 diabetes 4
- Key autoantibodies to test include:
- Islet cell autoantibodies (ICA)
- Glutamic acid decarboxylase autoantibodies (GAD65)
- Insulin autoantibodies
- Tyrosine phosphatase autoantibodies (IA-2 and IA-2β)
- Zinc transporter 8 autoantibodies (ZnT8) 3
- C-peptide measurement may help distinguish type 1 from type 2 diabetes in ambiguous cases 2
Monitoring Laboratory Tests
- HbA1c should be measured routinely every 3 months until acceptable targets are reached, then at least every 6 months 4, 1
- Treatment goals should be based on maintaining HbA1c concentrations <7% for many non-pregnant people with diabetes, with more stringent goals in selected individuals 4
- Higher target ranges are appropriate for children, adolescents, individuals with limited life expectancy, extensive comorbid illnesses, history of severe hypoglycemia, or advanced complications 4
- Patient-performed blood glucose monitoring is essential to achieve effective glycemic control and avoid both hyperglycemia and hypoglycemia 5
Screening for Complications
- Annual testing for albuminuria should begin in pubertal or post-pubertal individuals 5 years after diagnosis of type 1 diabetes 4
- Urine albumin should be measured using morning spot urine albumin-to-creatinine ratio (uACR) 4, 1
- If estimated glomerular filtration rate is <60 mL/min/1.73 m² and/or albuminuria is >30 mg/g creatinine, the uACR should be repeated every 6 months 4, 1
- First morning void urine sample should be used for measurement of albumin-to-creatinine ratio 4
Special Considerations
- HbA1c testing should only use NGSP-certified methods in accredited laboratories 1
- HbA1c may not be reliable in conditions affecting red blood cell turnover, such as sickle cell disease, pregnancy, hemodialysis, recent blood loss or transfusion, and erythropoietin therapy 2
- Laboratories should be aware of potential interferences, including hemoglobin variants that may affect HbA1c test results depending on the method used 4
- Blood ketone determinations should be used for diagnosis of diabetic ketoacidosis and may be used for monitoring during treatment 2
Common Pitfalls and Caveats
- Point-of-care HbA1c testing for diabetes screening and diagnosis should be restricted to FDA-approved devices at CLIA-certified laboratories that perform testing of moderate complexity or higher 4
- HbA1c does not provide a measure of glycemic variability or hypoglycemia, which are important factors in diabetes management 2
- For patients with conditions that interfere with HbA1c interpretation, alternative approaches such as self-monitoring of blood glucose or continuous glucose monitoring should be used 2
- Routine determination of genetic markers such as HLA genes or single nucleotide polymorphisms is of no value at this time for the diagnosis or management of patients with type 1 diabetes 4
- Timed collection for urine albumin should be done only in research settings and should not be used to guide clinical practice 4