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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Microsomal (TPO) Ab

Test Code(s): MAB / XTPO

CPT Code(s): 86376

Methodology: Chemiluminescent Immunoassay

Clinical Significance: Anti-thyroid peroxidase (TPO) antibodies are autoantibodies directed against the thyroid peroxidase enzyme. Historically, these antibodies were referred to as anti-microsomal antibodies because the antibodies bind to the microsomal portion of thyroid cells. Anti-TPO antibodies are detected in patients with autoimmune thyroid disease(Grave's and Hashimoto's). This antibody is very sensitive for the detection of autoimmune thyroid disease but lacks specificity. It is detected in increasing prevalence with age.

Days Performed: Mon-Fri, dayshift.

Turnaround Time: Stat: Not available stat.
Routine: Next working day.

Specimen Requirements

Specimen: Blood

Collection Container: Preferred: Red top
Also Acceptable: Red cap with yellow ring (SST)

Collection Volume: Preferred: 2 mL
Pediatrics: 1 mL

Sample Analyzed: Serum

Volume Required: Preferred: 0.3 mL
Pediatrics: 0.15 mL

Specimen Processing: Centrifuge within 2 hours of collection. If a complete barrier has not been formed, transfer cell-free serum to plastic vial. Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from UWHC Satellite lab location.

Outreach Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.

Unacceptable Criteria: Grossly hemolyzed specimens are not acceptable.

Stability: Ambient: Not acceptable
Refrigerated: 2 days at 2-8C
Frozen: Stable for longer periods at -20C or below. Avoid repeat freeze and thaw.


Expected Results:

1 year and up:  0 - 34 IU/mL



Test Limitations:

The Siemens Immulite 2000 method is used. Results obtained with different assay methods or kits cannot be used interchangeably.


Heterophilic antibodies in human serum can react with the immunoglobulins included in the assay components causing interference with in vitro immunoassays. Samples from patients routinely exposed to animals or animal serum products can demonstrate this type of interference potentially causing an anomalous result.

Autoantibodies may be found in less than 10% of the normal population at low levels and in patients with non-thyroidal illnesses, such as the inflammatory rheumatic diseases.

anti-Microsomal Antibody
anti- microsomal ab
Anti-TPO Antibody
thyroid antibody
thyroid peroxidase antibody

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