Turnaround times
The quoted turnaround time is from sample receipt in the laboratory, to results authorisation in the Laboratory Information Management system. The times do not include transport of specimen to the laboratory or the administrative process to print and post/email reports. Service users must allow for transport and reporting time when ordering tests.
Clinical background:
Thyroglobulin (Tg) is a glycoprotein of molecular weight 660,000. It is the principal iodoprotein of the thyroid gland and constitutes the majority of thyroid mass. The circulating levels of Tg tend to increase in a variety of thyroid diseases including toxic and non-toxic goitre, subacute thyroiditis, Graves’ disease, and carcinoma. In practice however, measurement of Tg is rarely useful in the diagnosis of disorders of thyroid function. The principal utlility of Tg measurements is in the monitoring of patients with a history of differentiated thyroid cancer who have undergone total thyroidectomy. Detectable Tg post-thyroidectomy suggests the presence of residual thyroid tissue or metastases. Serum Tg is monitored post-treatment as it is a useful marker of recurrence. Thyroglobulin autoantibodies (TgAb) are always measured alongside Tg, as TgAb can cause negative interference in immunometric Tg assays. Undetectable or low Tg concentrations should be intepreted with caution in TgAb positive samples as the measured concentration of Tg may be an under-estimate in such samples.
Specimen container paediatric:
Serum
Specimen container adult:
Serum
Minimum volume paediatric:
1.5 mL blood
Minimum volume adult:
2 mL blood
Sample stability:
2 days at 4 to 8°C
Transport requirements:
Ambient
Interpretation:
Interpretation of Tg and TgAbs:-
Thyroglobulin <0.2 ug/L:
Post-thyroidectomy, unstimulated thyroglobulin of less than 0.2 ug/L may be considered low risk for recurrence of differentiated thyroid cancer if there is no evidence of disease on imaging. See NICE NG230 for further details.
Thyroglobulin 0.2 to 1.0 ug/L:
Post-thyroidectomy, unstimulated thyroglobulin between 0.2 and 1.0 ug/L may be considered medium risk for recurrence of differentiated thyroid cancer. See NICE NG230 for further details.
Thyroglobulin >1.0 ug/L:
Post-thyroidectomy, unstimulated thyroglobulin greater than 1.0 ug/L may be considered higher
Thyroglobulin Antibodies <20 kU/L:
Undetectable thyroglobulin antibodies.
Thyroglobulin Antibodies 20 kU/L or greater:
Detectable thyroglobulin antibodies. Note that the presence of thyroglobulin antibodies can lead to falsely low thyroglobulin results.
Reference ranges:
In treated thyroid cancer patients, a thyroglobulin value of greater than 0.1 µg/L may be indicative of recurrent/residual thyroid cancer or persistent thyroid tissue.