Journal List > J Korean Endocr Soc > v.23(3) > 1003432

Huh, Suk, Kim, Choi, Son, Kim, and Kim: Clinical Usefulness of the Second Generation TSH-Binding Inhibitory Immunoglobulin Assay Using Recombinant Human TSH Receptor in Patients with Graves' Disease

Abstract

Background and Aim

Detection of TSH receptor antibody in patients with Graves' disease (GD) has been widely used in clinical practice. This has been performed mostly by commercial radio-receptor assays that measure TSH-binding inhibitory immunoglobulin (TBII) with using porcine TSH receptor as the ligand. To increase the sensitivity of the assay, many research groups have tried to replace the porcine source of TSH receptor with recombinant human TSH receptor. In this study we evaluated the clinical usefulness of the second generation TBII assay, which uses recombinant human TSH receptor, for making the diagnosis of GD, as compared to the conventional TBII assay.

Materials and Methods

We obtained sera from 76 patients with newly diagnosed or relapsing GD without or with less than 4 weeks of antithyroid drugs, and 54 patients with Hashimoto's thyroiditis who had not received thyroid hormone treatment or quit thyroid hormone more than 3 months before. TBII was measured by using both the conventional porcine TBII assay (pTBII) and the human recombinant TBII assay (hTBII). TBII was also measured in the sera from 66 healthy controls.

Results

The cut-off values of the pTBII and hTBII assay were defined as two geometric standard deviations from the geometric mean of the values in healthy controls, and these values were 10.8 IU/L and 1.0 IU/L, respectively. The sensitivity was 62% (47/76) for pTBII, as compared to 100% (76/76) for the hTBII, for diagnosing GD. Of the 54 patients with Hashimoto's thyroiditis, 3 (5.6%) and 7 (13.0%) patients had positive pTBII and positive hTBII, respectively.

Conclusion

These data showed that the hTBII assay was a comparable method in terms of the sensitivity for the diagnosis of GD, as compared to the pTBII assay. It can be suggested that this new hTBII assay, rather than the pTBII assay, should be more widely used as the first line diagnostic test for GD.

Figures and Tables

Figure 1
Cut-off value for pTBII (A) and hTBII (B) calculated from normal healthy controls. Cut-off value was defined as a geometric mean plus twice of a geometric standard deviation in healthy control. The cut-off values of pTBII and hTBII were 10.8 IU/L and 1.0 IU/L, respectively. Straight lines showed geometric mean of pTBII and hTBII, respectively. Dotted lines showed cut-off value of pTBII and hTBII, respectively.
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Figure 2
Comparison between pTBII and hTBII in patients with untreated Graves' disease.
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Figure 3
Distribution of (A) pTBII or (B) hTBII titer in patients with Hashimoto's thyroiditis without medication according to serum TSH level. Of 54 patients with Hashimoto's thyroiditis, 3 patients had positive TBII titers using pTBII and 7 patients had positive TBII titers using hTBII.
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Table 1
Comparison of patients with Graves' disease according to positivity of pTBII or hTBII titer
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* Fisher's exact test was used for gender, size of goiter, and ophthalmopathy. Wilcoxon's rank sum test was used for age at diagnosis, total T3, and free T4.

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