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Test ID IA2 Islet Antigen 2 (IA-2) Antibody, Serum

Reporting Name

IA-2 Ab, S

Useful For

Clinical distinction of type 1 from type 2 diabetes mellitus

 

Identification of individuals at risk of type 1 diabetes (including high-risk relatives of patients with diabetes)

 

Prediction of future need for insulin treatment in adult-onset diabetic patients

Specimen Type

Serum


Ordering Guidance


Islet cell antigen 2 (IA2) testing is available individually (this test) and with glutamic acid decarboxylase 65-kilodalton isoform (GAD65), insulin, and zinc transporter 8 (ZnT8) antibodies as a part of DBS1 / Diabetes Mellitus Type 1 Evaluation, Serum. The evaluation is most appropriate to order in the following clinical contexts: -Distinguishing type 1 (autoimmune) diabetes mellitus from type 2 diabetes mellitus -Identifying individuals at risk of type 1 diabetes (including high-risk relatives of patients with diabetes)  -Predicting future insulin requirement treatment in patients with adult-onset diabetes   Individual antibody testing would be more appropriate if 1, 2, or 3 of the analytes (GAD65, IA-2, insulin, ZnT8 antibodies) have already been tested and reported negative, and the provider wishes to test for the balance of remaining untested analytes only.

Specimen Required


Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1.5 mL


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reference Values

≤0.02 nmol/L

Reference values apply to all ages.

Day(s) Performed

Monday through Friday

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

86341

LOINC Code Information

Test ID Test Order Name Order LOINC Value
IA2 IA-2 Ab, S 81155-4

 

Result ID Test Result Name Result LOINC Value
89588 IA-2 Ab, S 81155-4

Clinical Information

Islet cell autoantibodies have been known to be associated with type 1 diabetes mellitus for many years. In recent years, several autoantigens against which islet antibodies are directed have been identified. These include the tyrosine phosphatase-related islet antigen 2 (IA-2), glutamic acid decarboxylase 65, zinc transporter 8, and insulin. One or more of these autoantibodies are detected in 96% of patients with type 1 diabetes and are detectable before clinical onset, as well as in symptomatic individuals. A serological study of 50 individuals with type 1 diabetes and 50 control subjects conducted simultaneously across 43 laboratories in 16 countries demonstrated a median sensitivity of 57% and a median specificity of 99% for IA-2 antibody in type 1 diabetes. Prospective studies in relatives of patients with type 1 diabetes have shown that development of 1 or more islet autoantibodies (including IA-2 antibody) provides an early marker of progression to type 1 diabetes. Autoantibody profiles identifying patients destined to develop type 1 diabetes are usually detectable before age 3. In one study of relatives seropositive for IA-2 antibody, the risk of developing type 1 diabetes within 5 years was 65.3%. Some patients with type 1 diabetes are initially diagnosed as having type 2 diabetes because of symptom onset in adulthood, societal obesity, and initial insulin-independence. These patients with "latent autoimmune diabetes in adulthood" may be distinguished from those patients with type 2 diabetes by detection of 1 or more islet autoantibodies (including IA-2).

Interpretation

Seropositivity for islet antigen 2 autoantibody (> 0.02 nmol/L) is supportive of:

-A diagnosis of type 1 diabetes

-A high risk for future development of diabetes

-A current or future need for insulin therapy in patients with diabetes

Clinical Reference

1. Shields BM, Shepherd M, Hudson M, et al; UNITED study team: Population-based assessment of a biomarker-based screening pathway to aid diagnosis of monogenic diabetes in young-onset patients. et al: Diabetes Care. 2017 Aug;40(8):1017-1025. doi: 10.2337/dc17-0224

2. Bingley PJ: Clinical applications of diabetes antibody testing. J Clin Endocrinol Metab. 2010 Jan;95(1):25-33

3. Bingley PJ, Bonifacio E, Mueller PW: Diabetes Antibody Standardization Program: first assay proficiency evaluation. Diabetes 2003 May;52(5):1128-1136 

4. Christie MR, Roll U, Payton MA, et al: Validity of screening for individuals at risk for type I diabetes by combined analysis of antibodies to recombinant proteins. Diabetes Care. 1997 Jun;20(6):965-970

5. Lampasona V, Petrone A, Tiberti C, et al: Zinc transporter 8 antibodies complement GAD and IA-2 antibodies in the identification and characterization of adult-onset autoimmune diabetes: Non Insulin Requiring Autoimmune Diabetes (NIRAD) 4. Diabetes Care. 2010 Jan;33(1):104-108

Report Available

3 to 9 days

Method Name

Radioimmunoassay (RIA)