Use of TSH-Receptor Antibodies (TRAb) in the assessment of new onset thyrotoxicosis within the North East of England.
Su A Tee1, David R Bishop2, Ahmed Al-Sharefi3, Owain Leng4 and Robert A James5
1Department of Diabetes and Endocrinology, Northumbria Healthcare NHS Foundation Trust, Newcastle, UK
2Department of Diabetes and Endocrinology, Sunderland Royal Hospital, Sunderland, UK
3Department of Diabetes and Endocrinology, Darlington Memorial Hospital, Darlington, UK
4Department of Diabetes and Endocrinology, South Tyneside General Hospital, South Tyneside, UK
5Department of Endocrinology, Royal Victoria Infirmary, Newcastle, UK
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Causes of hyperthyroidism include Graves’ disease (GD), toxic multinodular goitre and thyroiditis. British Thyroid Association guidelines recommend specialist referral once hyperthyroidism is diagnosed. TSH-receptor antibodies (TRAb) are more specific to GD than thyroid peroxidase antibodies (TPOAb). Regional guidelines recommend measuring TRAb in thyrotoxic patients. We aimed to assess TRAb use regionally in newly diagnosed thyrotoxicosis.
We conducted a retrospective case review of patients with newly detected thyrotoxicosis from 1st March-31st August 2015 from 4 endocrinology centres. TSH, fT4, fT3, TPOAb and TRAb values; the requester and date requested were recorded. Any thyroid uptake scans done; and final diagnoses were noted.
We analysed 209 records – 79% females (n=166), 21% males (n=43); the average age was 50.5 (17-96). 88.6% had TRAb requested. 76.2% requests were from endocrinologists, 15.7% from GPs, 5.9% from Biochemistry, and 2.2% from other physicians. 56.2% had positive TRAbs. The commonest diagnosis was GD (55.0%), followed by multinodular goitre (10.5%) and thyroiditis (8.1%). GD was diagnosed using TRAb in 81.7%; and using thyroid uptake scans in 6% (n=7). 2 patients had clinical features; in 12 patients, the reason for favouring a GD diagnosis was unclear. 19 patients (9%) were not referred to endocrinology. Average time between detection of thyrotoxicosis and TRAb request was 40 days (32-57 days). Time to TRAb request was shorter (average 9 days) if requested prior to referral to an endocrinologist. This lag was because most TRAb requests were only requested after referrals were received and reviewed by endocrinologists.
TRAb is commonly used regionally with good sensitivity and specificity. We propose that it should be added on by biochemistry labs in all newly thyrotoxic patients, as this could expedite diagnosis, minimising use of inappropriate antithyroid medications. Availability of results before endocrinology consultations would also facilitate prompt treatment and better communication with patients.