Use of anti thyroid hormone receptor antibody (TRAB) in Graves Disease
Khin Swe Myint, Gayathridevisa Shankargall Andappa, Ian MacFarlane, Mark Gurnell, Diana Wood, Khris Chatterjee & Helen Simpson
TRAB antibody is specific for diagnosis of Graves disease. We have conducted an audit to on our practice on parameters which TRAB could influence.
Method: TRAB (NR 01 IU/l) positive patients were identified from biochemistry laboratory form April 2003 to February 2004. Sixty case notes were randomly selected for reviewed. Data were analysed subsequently.
Result: 46 cases (77%) were female. Mean age was 42, range 6 to 78 years. Mean TRAB was (mean±sem) 9.12±1.24 IU/L. Fifty four and 6 patients were hyperthyroid and euthyroid at diagnosis respectively. In hyperthyroid group, there were 9 relapses for first (n=7) and second (n=2) times. Mean TRAB level in first time presenters was 6.97±0.07 compared with 7.46±0.34 IU/l in relapse cases. Among the euthyroid group, three were previously treated for thyrotoxicosis and reassessed because of pregnancy, one presented with goitre, one with thyroid ophthalmopathy and one had false positive TRAB who was diagnosed with orbital non-Hodgkins disease. Among 3 pregnant cases, one baby had neonatal thyrotoxicosis, the other 2 babies being euthyroid. Diagnosis was changed to Graves disease after TRAB assay in 6 patients. Fifteen patients (25%) had Graves ophthalmopathy (GO), but here was no difference in TRAB between non- GO cases (TRAB: GO 8.97±1.19; non GO 9.01±0.07 IU/l). Patients who were cured (no relapse after 1 year) had mean TRAB of 9.04±0.10 compared with not cure 5.74±0.24 IU/l, which was not statistically significant. There was a correlation between degree of thyrotoxicosis (T4 at diagnosis) and TRAB, R value 0.52, P<0.01.
Conclusions: TRAB assay is helpful in diagnosis of Graves disease when clinical feature are not conclusive. There is a correlation between TRAB and degree of thyrotoxicosis. TRAB is particularly useful during pregnancy as it may predict effect on the foetal/neonatal thyroid status. TRAB did not seem to predict chance of cure, or development of GO.