Clinical characteristics of Graves' orbitopathy in patients showing discrepancy between levels from TBII assays and TSI bioassay

Objective To investigate clinical characteristics of patients with Graves' orbitopathy (GO) who showed discrepancies between levels of thyroid-stimulating immunoglobulin (TSI) and thyrotropin-binding inhibitory immunoglobulin (TBII). Design Comparative case series. Patients A total of 317 patients with GO in whom Mc4-TSI and M22-TRAb (third-generation TBII) were measured simultaneously. Patients were divided into four groups according to TRAb levels as followings: Group 1, TBII and TSI= median, TSI= median; Group 4, both TBII and TSI >= median. Measurement Endocrine and ophthalmic clinical manifestations in each group. Results The median value of M22-TRAb was 6 center dot 11 IU/l and that of Mc4-TSI was 415 center dot 1 (SRR%). One hundred seventeen patients were classified as Group 1, 41 patients as Group 2, 41 patients as group 3 and 118 patients as group 4. Mean CAS was significantly higher in Groups 3 (2 center dot 2) and 4 (2 center dot 2) than in Groups 1 (1 center dot 6) and 2 (1 center dot 4; P=0 center dot 001, anova). Mean modified NOSPECS scores were significantly higher (P<0 center dot 001, anova) in Groups 3 (4 center dot 1) and 4 (4 center dot 1) than in Groups 1 (3 center dot 1) and 2 (2 center dot 3). The proportion of patients with hyperthyroidism was larger in Group 2 (85 center dot 4% [35/41 patients]) than in Group 3 (48 center dot 8% [20/41 patients]; P=0 center dot 002). Conclusions GO is more active and severe in patients with predominant Mc4-TSI than in patients with predominant M22-TRAb. Patients with hyperthyroidism were more likely to be included with patients with predominant M22-TRAb than with predominant Mc4-TSI.