Clotted blood tube
(Serum gel separator clot activator tube)
Minimum blood volume: 5 mL
Paediatric clotted blood tube
Number of vials: 2
Minimum blood volume: 1.6 mL
| Health subjects: | 3.5 - 77 µg/L |
| Post total thyroidectomy: | < 0.2 µg/L |
(Source: from manufacturer's kit insert)
Detection of tumour recurrence in thyroid cancer
Investigation of suspected thyroiditis or thyrotoxicosis factitia
Sensitive Tg assay with a functional sensitivity of 0.1 µg/L allows early detection of disease relapse in monitoring patients with thyroid cancer after ablative treatment using unstimulated thyroglobulin test.
Undetectable Tg levels are found after surgical thyroidectomy and thyroid radio-ablation, e.g. for thyroid cancer or hyperthyroidism. In these situations, Tg measurements may be useful in therapeutic monitoring.
Detectable levels in patients with thyroid cancer who have had a total thyroidectomy (and who should cease thyroid replacement therapy for 2 weeks prior to testing) indicates the presence of residual tumour.
Stimulation with recombinant TSH prior to testing has been recommended. Levels in thyroiditis and thyrotoxicosis are high, but if thyrotoxicosis is due to self-medication with thyroid hormone, the level is suppressed.
High Tg levels occur in true hyperthyroidism, while levels are low in factitious hyperthyroidism, e.g. due to synthetic T4 or T3 ingestion.
Individuals with congenital hypothyroidism due to thyroid agenesis have essentially undetectable serum Tg levels, and measurement of Tg levels may be a useful adjunct in the evaluation of neonatal hypothyroidism.
Circulating anti-Tg antibodies often occur in patients with autoimmune thyroiditis and in normal individuals without clinical thyroid disease. These antibodies may interfere with Tg assay and should be considered if assay results do not concur with clinical findings. Critical samples should be screened for the presence of anti-Tg antibodies before interpretation of results.