Third-Generation Elisa Thyrotropin-Receptor Antibody Levels as an Adjuvant Tool to Guide Management of Patients with Graves Orbitopathy

Abstract

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. 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. 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. 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.