Endocrine Abstracts

Background: TSH receptor antibody (TRAb) measurement, with a sensitivity of >97% and specificity of 100%, is considered the gold standard investigation for diagnosing Graves’ disease (GD).

Aim: To evaluate clinical diagnosis of GD or non- GD hyperthyroidism at a University Teaching Hospital compared to TRAb result.

Methods: Electronic records of patients who had a TRAb measurement between December 2009 and October 2015 were studied retrospectively for a pre-TRAb clinical diagnosis of GD or non-GD. We examined descriptive statistics and binary classification tests; Fisher exact test was used to analyse contingency tables.

Results: We identified 316 patients seen in the Endocrinology service aged 18–89 years with a mean ± standard error of 45.2±2.5 years; 247 (78%) were women. A clear pre-test clinical diagnosis was identified in 160 patients; the remaining 156 patients had differential diagnoses and were excluded for this analysis. Of the 166 patients, a clinical diagnosis of GD was identified in 93 patients, of which 67 were TRAb-positive, 19 were TRAb-negative and 7 were TRAb-borderline; 67 patients had a pre-test clinical diagnosis of non-GD, of which 47 were TRAb-negative, 15 TRAb-positive and 5 TRAb-borderline. After excluding TRAb-borderline patients, clinical diagnosis had a sensitivity of 82%, specificity 71%, positive predictive value 78%, negative predictive value 76%, false negative rate 18%, and false positive rate 29% (P < 0.0001). Incorrect initial clinical diagnoses were corrected at subsequent appointments based on the TRAb result.

Conclusion(s): Clinicians were liable to incorrectly make an initial clinical diagnosis of non-GD in 1 in 5 patients with TRAb-positive GD, whilst 3 in 10 patients with TRAb-negative non-GD were incorrectly mislabelled as GD clinically. The TRAb test can help reduce the number of incorrect or unknown diagnoses in the initial clinical assessment of patients presenting with hyperthyroidism.