6502 Comparing TBII vs TSI Assays at University Hospital; A Quality Improvement Project

Abstract Disclosure: L.E. Chozet: None. G. Le: None. M.A. Escobar Vasco: None. Radionuclide uptake and scan in the setting of thyrotoxicosis is considered the gold standard test to diagnose Graves' disease (GD). However, TSH-receptor antibodies (TRAB) tests are now being used as optional first-line tests given their widespread availability and cost-effectiveness. Thyrotropin-binding inhibitory immunoglobulin (TBII) and thyroid-stimulating immunoglobulin (TSI) assays are commonly obtained in patients admitted with thyrotoxicosis. Both assays are readily available at our institution. Our project aimed to further review and compare these two assays. To determine turnaround times of these assays at our institution, as well as cost-effectiveness of ordering both TBII and TSI assays vs only ordering one assay. We did a retrospective evaluation of 27 patients with lab evidence of thyrotoxicosis at University Hospital between April 2022, and May 2023 who were tested with both TBII, TSI assays simultaneously during their hospital stay to compare their concordance. We then compared turnaround times in days for laboratory results to be available. TBII, TSI assays are not done in-house. They are instead sent to an outside laboratory. Our hospital pathology services provided us with information regarding lab costs. We investigated which assay is more cost-effective. Based on our data, TBII and TSI were concordant in almost all patients evaluated (26 out of 27). Ordering TBII as the first initial test for GD is more cost-effective than ordering both TSI, TBII simultaneously. Our findings are consistent with previous studies, which suggest that ordering both assays (TBII and TSI) could be reserved for patients where the diagnosis of GD is not clear. Presentation: 6/3/2024