Quantitative Enzyme-Linked Immunosorbent Assay
Useful to establish autoimmune etiology in previously diagnosed T1DM.
Diabetes mellitus (DM) refers to a group of metabolic disorders characterized by hyperglycemia that results from defects in insulin secretion, insulin action, or both. Type 1 DM (T1DM) is less common than type 2 DM (T2DM) and is characterized by insulin deficiency, often resulting from the autoimmune-mediated destruction of insulin-producing cells. The detection of diabetes-associated autoantibodies confirms an autoimmune etiology for that individual.
Indications for Insulin Antibody Testing
GAD, glutamic acid decarboxylase antibody; IA-2, islet antigen-2; IAA, insulin antibody; ICA, islet cell cytoplasmic antibody; LADA, latent autoimmune diabetes of the adult; ZnT8, zinc transporter 8 antibody
Diabetes Mellitus Type 1 Overview
1.25 million in the United States
Age of Onset
Most common in children but can develop in individuals of any age, especially in late 30s or early 40s
- Excessive thirst, hunger, and urination
- Fatigue, nausea, blurred vision
- Unexplained weight loss
- Obesity is rare upon initial diagnosis
- May have other autoimmune disorders
- Caused by autoimmune-mediated destruction of insulin-producing beta cells of the islets of Langerhans in the pancreas
- Five major autoantibodies of diagnostic interest
- Glutamic acid decarboxylase (GAD)
- Insulin antibodies (IAA)
- Islet antigen-2 (IA-2)
- Islet-cell antibodies (ICA)
- Zinc transporter 8 (ZnT8)
- Antibodies may be present in individuals years before the onset of clinical symptoms
- Presence in individuals with diabetes confirms an autoimmune etiology
Moderate sensitivity, high specificity in newly diagnosed T1DM
- Presence of antibodies may decrease with long-term disease
- Insulin antibody testing loses specificity once patient has been on exogenous insulin for >2 weeks
- Presence of multiple insulin antibodies (GAD, IA-2, IAA, ICA, and ZnT8) is predictive of T1DM
- If one autoantibody is found, others should be assayed; the risk of T1DM increases (>90%) if an individual tests positive for two or more autoantibodies
- For further risk stratification, HLA-DR or HLA-DQ genotyping may be helpful
- Negative test results do not rule out autoimmune diabetes; autoantibody response varies by individuals
- Presence of a single autoantibody in the absence of clinical symptoms has low predictive value (1-2% in healthy individuals)
- Not all individuals with antibodies will develop T1DM
- Do not use to monitor or diagnose T1DM
- IAA test does not differentiate between antibodies specific for endogenous and exogenous forms of insulin
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