What are the steps for testing and managing diabetes mellitus (DM) type 1?

Testing and Managing Type 1 Diabetes Mellitus

The diagnosis of type 1 diabetes requires confirmation of hyperglycemia through standardized glycemic tests along with evidence of autoimmune etiology through autoantibody testing, followed by immediate insulin therapy initiation to prevent life-threatening complications. 1, 2

Diagnostic Process for Type 1 Diabetes

Step 1: Initial Glycemic Testing

• Diagnose using one of these criteria:
  • Fasting plasma glucose (FPG) ≥126 mg/dL (7.0 mmol/L) after at least 8 hours fasting
  • 2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) during 75g oral glucose tolerance test (OGTT)
  • Random plasma glucose ≥200 mg/dL (11.1 mmol/L) with classic symptoms (polyuria, polydipsia, weight loss)
  • HbA1c ≥6.5% (48 mmol/mol) using NGSP-certified method 1

Step 2: Confirmation Testing

• Repeat testing on a different day to confirm diagnosis, unless:
  • Patient has classic symptoms of hyperglycemia with random glucose ≥200 mg/dL
  • Patient presents with diabetic ketoacidosis (DKA)
  • Patient has unequivocal hyperglycemic crisis 1

Step 3: Autoimmune Marker Testing

• Test for islet autoantibodies to confirm autoimmune etiology:
  • Glutamic acid decarboxylase (GAD)
  • Islet antigen 2 (IA-2)
  • Zinc transporter 8 (ZnT8)
  • Insulin autoantibodies (if not already on insulin) 1, 2

Step 4: C-peptide Assessment

• Measure C-peptide levels to assess endogenous insulin production
• Values <200 pmol/L (<0.6 ng/mL) suggest type 1 diabetes 2

Initial Management After Diagnosis

Step 1: Immediate Insulin Initiation

• Start insulin therapy immediately after diagnosis
• Use multiple daily injection regimen or insulin pump therapy
• Typically includes:
  • Rapid-acting insulin (e.g., insulin aspart) before meals
  • Intermediate or long-acting insulin for basal coverage 3

Step 2: Education and Self-Management Training

• Provide comprehensive diabetes education including:
  • Blood glucose monitoring techniques
  • Insulin administration
  • Hypoglycemia recognition and treatment
  • Sick day management
  • Nutritional guidance 1

Step 3: Blood Glucose Monitoring

• Establish self-monitoring of blood glucose (SMBG) routine
• Target preprandial glucose: individualized based on age and risk factors
• Monitor postprandial glucose when there's discrepancy between preprandial values and A1C 1

Step 4: Screening for Associated Conditions

• Test for additional autoimmune conditions:
  • Thyroid function tests and thyroid antibodies (anti-TPO, anti-thyroglobulin)
  • Celiac disease screening with IgA tissue transglutaminase (tTG) antibodies
  • Consider screening for other autoimmune conditions based on symptoms 1

Ongoing Management and Monitoring

Glycemic Monitoring

• Check HbA1c every 3 months until target achieved, then at least every 6 months
• Target HbA1c <7% for most adults, with more stringent or relaxed goals based on individual factors 1

Complication Screening

• Annual screening for microvascular complications:
  • Nephropathy: Urine albumin-to-creatinine ratio (uACR) starting 5 years after diagnosis
  • Retinopathy: Annual dilated eye examination
  • Neuropathy: Comprehensive foot examination 1, 4

Ongoing Autoimmune Screening

• Recheck thyroid function every 1-2 years or sooner if symptoms develop
• Repeat celiac disease screening within 2 years of diagnosis and again after 5 years 1

Special Considerations

Children and Adolescents

• Adjust blood glucose goals for children with frequent hypoglycemia
• Consider developmental stage when establishing treatment plans
• Screen for diabetes-related distress and mental health issues 1

Pregnancy Planning

• Target more stringent HbA1c goals (<6.0%) before and during pregnancy
• Intensify monitoring and insulin adjustments during pregnancy 1

Common Pitfalls to Avoid

1. Delayed diagnosis: Classic symptoms of polyuria, polydipsia, and weight loss should prompt immediate testing, not watchful waiting.

2. Misclassification: Don't rule out type 1 diabetes based on age or presence of obesity; autoantibody testing is essential for proper classification 1, 2.

3. Inadequate initial education: Comprehensive education at diagnosis is critical to prevent acute complications like DKA and severe hypoglycemia.

4. Missing associated autoimmune conditions: Always screen for thyroid disease and celiac disease, as they commonly co-occur with type 1 diabetes 1.

5. Overlooking psychosocial aspects: Address the emotional and social impact of diagnosis, especially in children and adolescents.