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

Abstract

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 value; Group 2, TBII ≥ median, TSI < median; Group 3, TBII < 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 6·11 IU/l and that of Mc4-TSI was 415·1 (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 (2·2) and 4 (2·2) than in Groups 1 (1·6) and 2 (1·4; P = 0·001, ANOVA). Mean modified NOSPECS scores were significantly higher (P < 0·001, ANOVA) in Groups 3 (4·1) and 4 (4·1) than in Groups 1 (3·1) and 2 (2·3). The proportion of patients with hyperthyroidism was larger in Group 2 (85·4% [35/41 patients]) than in Group 3 (48·8% [20/41 patients]; P = 0·002). 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.