Diagnosis and Management of Type 1 Diabetes Mellitus

Diagnostic Approach

The American Diabetes Association recommends measuring plasma glucose immediately for patients with suspected type 1 diabetes presenting with classic symptoms, with a random plasma glucose ≥200 mg/dL confirming the diagnosis without requiring additional testing 1, 2.
For Asian patients, a random plasma glucose ≥200 mg/dL with symptoms is diagnostic, and fasting plasma glucose ≥126 mg/dL or 2-hour post-75g glucose load ≥200 mg/dL also confirms diabetes 1, 2, 4, 5.

Type 1 diabetes should be staged based on autoantibody status and glycemic parameters, with Stage 1 being multiple islet autoantibodies with normoglycemia, Stage 2 being islet autoantibodies with dysglycemia, and Stage 3 being overt diabetes by standard criteria with symptoms 4, 5.

Single positive autoantibody is associated with a 15% risk of developing clinical diabetes within 10 years, while two or more positive autoantibodies are associated with a 70% risk within 10 years and 84% within 15 years 2, 6, 8, 9.

The American Diabetes Association recommends initiating insulin therapy immediately for patients with overt hyperglycemia at a starting dose of 0.3-0.4 units/kg/day total daily dose, with intensive glycemic control reducing microvascular and macrovascular complications 6.
For patients with positive autoantibodies but without overt diabetes, consider teplizumab therapy to delay progression to clinical disease, with longitudinal follow-up and repeated metabolic assessments essential to track disease progression 4, 5, 6.

Systematically screen for thyroid disease, celiac disease, and other autoimmune conditions soon after diagnosis, with measurement of antithyroid peroxidase antibodies and TSH, and testing IgA tissue transglutaminase antibodies with documentation of normal total serum IgA levels 6.

Do not repeat islet autoantibody testing for monitoring established type 1 diabetes, as there is no clinical utility outside research protocols, and C-peptide testing is useful in insulin-treated patients to assess residual β-cell function 4, 5, 3.

Recognize that insulin requirements may be intermittent rather than continuous in Asian patients with autoantibody-negative type 1 diabetes, and monitor closely for episodic DKA even during periods of apparent glycemic control 1, 2, 7.

Screening for islet autoantibodies should be offered to first-degree relatives of patients with type 1 diabetes, ideally in a research setting, with first-degree relatives having approximately 5% risk of developing type 1 diabetes, which is 15-fold higher than the general population 1, 10, 8.