Clinical Value of a Rapid Fully Automated Thyroid Autoantibody Assay in the Diagnosis and Management of Graves Disease

The most common cause of hyperthyroidism is Graves disease (GD) which is characterised by the presence of autoantibodies which binds to the TSH receptor (TRAb). Recently, a rapid, fully automated electrochemiluminescent immunoassay Elecsys (R) Anti-TSHR for detection of autoantibodies to TSH receptor was made available for routine clinical use. The objective of this study is to evaluate this assay and to determine the sensitivity, specificity and cut-off value. Interassay and total imprecision (CV) were determined at 3.78-7.02 IU/L and 13.5-21.2 IU/L respectively. A total of 124 samples which comprised of 46 GD, seven Hashimoto thyroiditis (HD), 11 non autoimmune nodular goitre (NAG), 2 thyroid cancers (Ca) and 58 normal controls were retrospectively analysed to determine the sensitivity, specificity and cut-off value. Inter-assay CV's were 2.4% at a concentration of 3.90 IU/L (range: 3.78-7.02 IU/l) and 0.8% at 20.80 IU/L (range: 13.5-21.2 IU/l). Total imprecision was 3.8% at a concentration of 3.80 IU/L (range: 13.5-21.2 IU/l) and 1.0% at 20.8 IU/L (range: 13.5-21.2 IU/l). The ROC analysis of patients with GD, other thyroid disorders and normal controls revealed that the highest sensitivity (94%) and specificity (98%) were seen at cut-off value of 1.69 IU/L. Positive predictive value (PPV) and negative predictive value (NPV) was 95% and 94% respectively. At this derived cut-off value of 1.69 IU/L, we found that the sensitivity of TRAb positivity within the group of 29 newly diagnosed GD patients was 94%. Our results demonstrate that this fully automated assay with testing time of 27 minutes has high sensitivity in detecting GD and high specificity for discriminating other thyroid disease and represent major improvement in the diagnosis and management of patients with thyroid diseases.