76. Gene expression profile of temporal artery tissue and whole blood in giant cell arteritis

Background: Giant cell arteritis (GCA) is a systemic vasculitis affecting adults over age 50. Diagnosing GCA is notoriously challenging, as there are no reliable blood biomarkers and temporal artery biopsy (TAB) has a sensitivity of only approximately 80%. Thus, patients suffer both from missed diagnoses and over-treatment. This study seeks to identify differentially expressed transcripts in the blood and TAB of patients with GCA relative to controls, as determined by RNA-sequencing (RNA-Seq). Methods: Blood (PAXgene tubes) and formalin-fixed paraffin-embedded (FFPE) TAB tissue from patients undergoing TAB for suspected GCA were evaluated by RNA-Seq. Samples representative of biopsy positive GCA, biopsy negative GCA (negative biopsy but clinically diagnosed with GCA), polymyalgia rheumatica (PMR), non-vasculitic ischemia, other inflammatory diseases, and healthy controls (patients who underwent temporal artery biopsy but were not diagnosed with any disease) were included. Significantly differential expressed genes (DEGs) were considered as having a fold change (FC) > 1.5 and a false discovery rate (FDR)