Endocrine Abstracts

The performance of a commercial method (RSR) for measuring TBII was compared prospectively with an in-house method. TBII data were correlated with clinical information available at the time of clinic attendance and with the ultimate diagnosis in the light of additional independent information (isotope scan, thyroid microsomal antibodies, response to treatment). Serum samples were collected prospectively from subjects attending an endocrine clinic and from normal subjects (group 1 n=24). Parients were subdivided into 4 groups. Group 2 (n=13): new untreated patients with thyrotoxicosis whom the endocrinologist was confident had Graves' disease on clinical grounds (diffuse goitre and/or clinical evidence of thyroid eye disease). Group 3 (n=4): Patients with Graves' disease, thyroid eye disease and pre-tibial myxoedema. Group 4 (n=20): Patients with non-autoimmune thyrotoxicosis (toxic multinodular goitre, toxic adenoma, thyroiditis). Group 5 (n=15): New untreated patients with thyrotoxicosis, where the endocrinologist was uncertain of the precise aetiology after a thorough clinical evaluation (history and examination).

On the basis of Groups 1 to 4, which were pre-diagnosed subjects, the clinical sensitivity and specificity of the RSR assay was 88% and 100% respectively. The corresponding values for the in-house method were 71% and 100%. If patients in Group 5 are included the clinical sensitivity and specificity for the RSR method 75% and 100% compared to 65% and 100% of the in-house method.

In conclusion, the RSR kit provides a simple, rapid and reliable method of measuring TBII, with excellent clinical specificity and good clinical sensitivity.