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Test Directory

Test Directory Insulin Autoantibody

Insulin Autoantibody

Test Summary

In patients who have not yet been treated with insulin but have symptoms suggestive of diabetes or a genetic predisposition based on family history, this test can be used to 1) distinguish among type 1 diabetes mellitus (autoimmune), type 2 diabetes mellitus, and atypical forms of diabetes, such as latent autoimmune diabetes in adults (LADA); or 2) to evaluate risk of future type 1 diabetes. This test may also be useful when evaluating patients for very rare autoimmune hypoglycemic syndrome [1-3].

In patients who have already been treated with insulin, insulin autoantibodies are usually of no clinical significance. Therefore, insulin antibody testing is generally not indicated for these patients. However, in rare cases, patients with suspected type 2 diabetes who have failed hypoglycemic treatment are tested and subsequently diagnosed with type 1 diabetes [3]. This test is generally used along with other diabetes-related autoantibody tests such as GAD-65 Antibody (test code 34878) and IA-2 Antibody (test code 36177); all 3 antibodies can be ordered together as test code 10584. ZnT8 Antibody (test code 93022) may also be a useful additional test.

Testing for multiple diabetes-related antibodies may be helpful in diagnosis, because some forms of type 2 diabetes may initially resemble type 1 or have a positive result on testing for one of these autoantibodies [4]. The higher the number of autoantibodies that are positive, the higher the likelihood of an autoimmune cause (type 1 or LADA) for diabetes mellitus.

For patients who do not yet have clinically apparent diabetes, a higher number of positive autoantibody tests predicts a higher risk of developing type 1 diabetes in the future [1]. Rarely, insulin antibodies can take on a shape that resembles insulin closely enough to stimulate the insulin receptor, leading to hypoglycemia. The presence of insulin antibody in a hypoglycemic patient who has not previously been treated with insulin is suggestive of, but not definitive for, this rare syndrome [2].

Test results should be interpreted in the context of pertinent clinical and family history and physical examination findings.

References
1. Winter WE, et al. Clin Chem. 2011;57:168-175.
2. Censi S, et al. Ann Transl Med. 2018;6:335. doi: 10.21037/atm.2018.07.32
3. Pihoker C, et al. Diabetes. 2005;54(Suppl 2):S52-S61.
4. Wentworth JM, et al. Nat Rev Endocrinol. 2009;5:483-489.

Aliases

Specimen Collection

Special Instructions

N/A

Preferred Specimen

1 mL serum

Minimum Volume

0.2 mL

Instructions

N/A

Patient Preparation

N/A

Storage

N/A

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 28 days
Refrigerated: 28 days
Frozen: 90 days

Limitations

In diabetic children <14 years of age (identified by urine screening), the frequency of insulin antibodies (IAA) and islet cell antibodies (ICA) are 43-56% and 84%, respectively; the frequency of both is 40%, and the frequency of one or both is 88%.4 In the same study, cohorts using ICA, GAD-65 antibodies and IAA, sensitivities and specificities are 93% and 93% for any positive, respectively, and 39% and >99%, respectively, for all positives. IAA are found at onset of diabetes in only 4% of adults, but are universally present in diabetic children <4 years old at onset. The predictive value of both tests (ICA and IAA) is 60-77% in first-degree relatives of patients with IDDM for the development of IDDM in 5-10 years.

Other Acceptable Specimens

N/A

Unacceptable Specimens

N/A

Order Code

INSAB

EPIC (Premier) Code

LAB1358

Includes

N/A

CPT Code

86337

Billing Code

670105

CPT Statement

Methodology

Radiobinding Assay (RBA)

FDA Status

FDA Approved

Physician Attestation of Informed Consent

N/A

Testing Laboratory

Quest Diagnostics Nichols Institute
33608 Ortega Highway
San Juan Capistrano CA, 92675

Department

Reference Testing

Reference Range

<0.4 U/mL

Setup Schedule / Expected Turnaround Time

Evening 3 days a week.