Objective: When assessing patients with Graves orbitopathy (GO) in an endocrinology outpatient setting, it is desirable to have a diagnostic laboratory tool to complement the clinical activity score (CAS) in distinguishing patients with moderate-severe active GO requiring high-priority ophthalmological care from those with mild or inactive GO who can be electively scheduled and to asses response to treatment.
Methods: A retrospective study was conducted to evaluate the correlation between thyrotropin-receptor antibody (TRAb)-Fast-enzyme-linked immunosorbent assay (ELISA) results and CAS in patients with GO seen at a tertiary referral center between 2000 and 2009. TRAb levels were quantified using a commercial third-generation TRAb-specific ELISA. Other variables analyzed included smoking status, gender, age, and thyroid-stimulating hormone level.
Results: Fifty-five patients with GO had a documented CAS within a mean of 22 days from the recorded TRAb level determined by TRAb-Fast-ELISA. An increase in TRAb-Fast-ELISA of 1 unit was associated with a 15% (95% confidence interval, 7-24%) increase in the odds ratio of elevated CAS. A TRAb-Fast-ELISA result ≥10 as a diagnostic tool to predict a CAS ≥3 was assessed and was found to have a specificity of 86.7% and a sensitivity of 87.2% for moderately severe GO.
Conclusion: Our results demonstrate the ability to predict a patient's GO activity level by antibody titer. A TRAb-Fast-ELISA result ≥10 can be used as a complementary diagnostic tool to predict a CAS ≥3.