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Test Code OH21 21-Hydroxylase Antibodies, Serum

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

21-Hydroxylase Ab, S

Specimen Type


Specimen Required

Collection Container/Tube: 

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Reject Due To


Mild OK; Gross reject


Mild OK; Gross reject


Mild OK; Gross OK



Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 14 days
  Refrigerated  7 days

Specimen Minimum Volume

0.19 mL

Day(s) and Time(s) Performed

Thursday; 2 p.m.

Specimen Retention Time

2 weeks

Analytic Time

2 days

Reference Values

<1 U/mL

Reference values apply to all ages.

Useful For

Investigation of adrenal insufficiency


Aid in the detection of those at risk of developing autoimmune adrenal failure in the future

Method Name

Immunoabsorption Assay

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
OH21 21-Hydroxylase Ab, S In Process


Result ID Test Result Name Result LOINC Value
81970 21-Hydroxylase Ab, S 17781-6

Clinical Information

Chronic primary adrenal insufficiency (Addison disease) is most commonly caused by the insidious autoimmune destruction of the adrenal cortex and is characterized by the presence of adrenal cortex autoantibodies in the serum. It can occur sporadically or in combination with other autoimmune endocrine diseases, that together comprise Type I or Type II autoimmune polyglandular syndrome (APS).


The microsomal autoantigen 21-hydroxylase (55 kilodalton) has been shown to be the primary autoantigen associated with autoimmune Addison disease. 21-Hydroxylase antibodies are markers of autoimmune Addison disease, whether it presents alone, or as part of Type I or Type II (APS).


Positive results (≥1 U/mL) indicate the presence of adrenal autoantibodies consistent with Addison disease.


Lipemic or grossly hemolyzed serum should not be used in this assay. Interpretation of test results requires consideration of other factors such as the clinical status of the patient, other test results, etc.

Clinical Reference

1. Husebye ES, Allolio B, Arlt W, et al: Consensus statement on the diagnosis, treatment and follow-up of patients with primary adrenal insufficiency. J Intern Med 2014 Feb;275(2):104-115

2. Tanaka H, Perez M, Powell M, et al: Steroid 21 hydroxylase autoantibodies: measurements with a new immunoprecipitation assay. J Clin Endocrinol Metab 1997;82:1440-1446

Method Description

Calibrators, controls, and patient specimens are incubated overnight with I(125) 21-hydroxylase. Antibody, if present, binds to the 21-hydroxylase during this time. Protein A is added to precipitate the antibodies present, the assay tubes are centrifuged, and the pellet is counted. The amount of radioactivity in the pellet is directly proportional to the amount of antibody contained in the specimen.(Package insert: 21-Hydroxylase [21-OH] Antibody Kit. Kronus, San Clemente, CA)

Supportive Data

Reagent Manufacturer's Data


Patient Group

Positive Rate

Healthy blood donors


Isolated Addison's disease


Addison's disease due to tuberculosis


APS type I


APS type II


Insulin dependent diabetes mellitus


Noninsulin dependent diabetes mellitus


Grave's disease


Hashimoto's disease


Myasthenia gravis



Mayo Data


Patient Group

Positive Rate

Normals from Mayo NV Study


+ Insulin Antibody


+ Thyroid stimulating Immunoglobin


+ Antinuclear Antibodies


+ Rheumatoid Factor