From Monday 10th February 2020 Awanui Labs (CSCL) and Canterbury Health Laboratories (CHL) will no longer report anti-thyroglobulin (anti-Tg) as part of the routine thyroid antibody screen.
Given the superior clinical utility of anti‐thyroid microsomal (anti‐TPO) antibodies, when thyroid antibodies are ordered the laboratory will perform anti‐thyroid microsomal (anti‐TPO) antibodies only.
The most common cause of thyroid dysfunction is autoimmunity, with autoimmune thyroid disease the most common autoimmune condition in our community. Thyroid related autoantibodies are useful in supporting autoimmunity as the underlying mechanism, particularly where the cause of abnormal thyroid function tests is unclear. In patients with hypothyroidism, anti‐thyroid microsomal or peroxidase antibodies (anti‐TPO) is the more specific and helpful autoantibody to order when autoimmune
(Hashimoto’s) thyroiditis is suspected. However, like many autoantibodies, it can be detected in many patients years before the onset of clinically overt hypothyroidism.
Although commonly ordered, anti‐thyroglobulin (anti-Tg) antibodies are less specific for the diagnosis of autoimmune thyroid disease.
Measurement of thyroglobulin (Tg) is used to monitor patients with differentiated thyroid cancer. However, the presence of anti-Tg antibodies in these patients can interfere with the measurement of Tg. For this reason, anti-Tg will continue to be measured at the same time as Tg in these
patients. When Tg is requested, the anti-Tg test is always added automatically and there is no requirement to specify a request for anti-Tg on the request form.
For any queries, please contact:
- Dr Richard Steele
- Clinical Immunologist, Southern Community Laboratories
- richard.steele@wellingtonscl.co.nz
- Dr Richard King
- Clinical Director – Biochemistry and Genetics, Canterbury Health Laboratories
- richard.king@cdhb.health.nz