Exagen Inc. develops and commercializes various testing products based on its Cell-Bound Complement Activation Products technology under the AVISE brand in the United States. It enables rheumatologists to enhance care for patients through the diagnosis, prognosis, and monitoring of complex autoimmune and autoimmune related diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Its lead testing product is AVISE CTD that enables differential diagnosis for patients presenting with symptoms indicative of various connective tissue diseases (CTDs) and other related diseases with overlapping symptoms. The company's products also comprise AVISE Lupus that measures activation of the complement system by quantifying the level of B-cell C4d and erythrocyte bound C4d in the patient's blood; and AVISE APS, which consists of a panel of eight autoantibody tests that aids in the diagnosis and management of APS. In addition, it provides AVISE SLE Prognostic, a ten-biomarker panel of autoantibodies for assessing the potential for complications affecting the kidney, brain, and cardiovascular system; AVISE Vasculitis AAV, which utilizes a testing panel of individual analytes designed to provide physicians with rapid and reliable results in the assessment and monitoring of anti-neutrophil cytoplasmic antibody; AVISE Anti-CarP test, which identifies RA patients with severe disease requiring aggressive therapy, such as anti-TNF biologics; and AVISE PC4d that measures platelet- bound C4d. Further, the company offers AVISE SLE Monitor, a six-biomarker blood test; AVISE MTX, a patented and validated blood test that measures levels of MTXPG; and AVISE HCQ, a blood test designed to help rheumatologists objectively monitor levels of hydroxychloroquine. The company was formerly known as Exagen Diagnostics, Inc. and changed its name to Exagen Inc. in January 2019. Exagen Inc. was incorporated in 2002 and is headquartered in Vista, California.