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PTD - 295

Test Directory -  Thyroid Antibodies

Synonyms

Thyroid microsomal or peroxidase antibody, TPOAb

Clinical Indications

Thyroid antibody (TAb) is a sensitive marker of immune thyroid damage (which is most extreme in Hashimoto's thyroiditis). Positive TAb indicates a 4-5 fold increase in the likelihood of developing overt hypothyroidism and also indicates an increased chance of post-partum thyroid dysfunction or amiodarone-induced hypothyroidism. Thyroid antibody levels do not correlate with degree of thyroid disease and cannot be used to monitor therapy.

Part of Profile

Thyroid Function Tests

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's)

Availability

On request. TAb is automatically measured on new cases of compensated hypothyroidism where TSH >6.9 mU/L or in cases of compensated hypothyroidism with persistently raised TSH of  between 4.2 and 6.9 mU/L

Specific Criteria

Assessment of compensated hypothyroidism.

Patient Preparation

 

None required.

Limitations

 

Thyroid antibody levels do not correlate with degree of thyroid disease and cannot be used to monitor therapy.

Turnaround Time

Same day

Specimen

Serum

Volume

0.5 ml

Container

Yellow top (SST) tube or

Paediatric orange top (lithium-heparin)

Causes for Rejection

Unlabelled sample

Interpretation

In compensated (sub-clinical) hypothyroidism, positive TAb strongly supports a decision to treat with thyroxine. TAb has no role in monitoring thyroid treatment and should not be repeated once positive.

Lab Handling

Processing: Analysed from primary tube and stored at 4C in the cold room (CB23)

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Version 1.0 / August 2014                                                                                                       Approved by: Consultant Biochemist