SUVmax, extraocular muscle diameter, and TRAb in assessing inflammatory activity of thyroid-associated ophthalmopathy

Abstract:

AIM: To investigate the value of maximum standardized uptake value(SUV_max), extraocular muscle(EOM)diameter, and thyroid stimulating hormone receptor antibody(TRAb)in evaluating inflammatory activity in thyroid-associated ophthalmopathy(TAO).

METHODS: TAO patients underwent orbital ^99mTc-DTPA SPECT/CT imaging at the Affiliated Hospital of Panzhihua University between January 2023 and December 2024 were retrospectively enrolled. According to the clinical activity score(CAS), patients were classified into an active group and an inactive group. SUV_max and EOM were independently measured by three nuclear medicine physicians, and the mean values were used for analysis. Serum TRAb levels from TAO patients were measured using a fully automated electrochemiluminescence immunoassay analyzer. Nonparametric tests were used to compare differences between the two groups. Spearman correlation analysis was performed to assess the correlations of CAS with SUV_max, EOM, and TRAb. Using CAS as the reference standard, receiver operating characteristic(ROC)curves were plotted to evaluate the diagnostic performance of SUV_max, EOM, and TRAb, as well as their combination. Intraclass correlation coefficient(ICC)was used for reliability analysis to evaluate the consistency of SUV_max and EOM among the 3 measurers.

RESULTS: A total of 99 patients(198 eyes)with TAO were enrolled in this study, including 38 males and 61 females, aged 16-74(46.92±11.84)y. The active group comprised 46 patients(92 eyes), aged 16-71(48.40±12.02)y, with 25 males and 21 females. The inactive group included 53 patients(106 eyes), aged 17-74(45.46±11.59)y, consisting of 13 males and 40 females. There were no statistically significant differences between the two groups in terms of gender and age(P>0.05). Statistically significant differences were observed in SUV_max, EOM, and TRAb. Compared with the inactive group, the active group showed higher SUV_max, EOM, and TRAb levels(all P<0.01). Correlation analysis showed that CAS was positively correlated with SUV_max, EOM, and TRAb(r=0.734, 0.622, and 0.404, respectively, all P<0.01). ROC curves were plotted using CAS as the reference standard, and the AUCs for SUV_max, EOM, TRAb, and their combined diagnosis were 0.874, 0.797, 0.715, and 0.892, respectively. The ICC of SUV_max and EOM were 0.925(95%CI: 0.901-0.948, P<0.001)and 0.943(95%CI: 0.907-0.964, P<0.001)respectively.

CONCLUSION: Beyond CAS, there is a need to identify objective imaging and serological biomarkers. Measurements of SUV_max and EOM provide visualized and quantifiable tools for assessing TAO activity, and their combination with TRAb can further improve the accuracy of activity assessment.