Exagen is a specialty diagnostics company focused on autoimmune disease testing, primarily serving rheumatologists across the U.S. Its flagship product, AVISE CTD, is a comprehensive blood test that helps clinicians diagnose and differentiate among connective tissue diseases including SLE and RA. AVISE CTD is built around Exagen's proprietary CB-CAPs technology, which measures complement activation products bound to blood cells and is more sensitive for SLE than conventional standard-of-care tests. In 2025, Exagen expanded AVISE CTD with eight new biomarkers — including T-cell biomarkers for SLE and seronegative RA markers — bringing RA patient identification to roughly 85%, up from ~70% with conventional testing. AVISE CTD accounts for roughly 91% of revenue, with a suite of nine additional AVISE-branded tests for disease monitoring and prognosis contributing the remainder. All testing is performed at Exagen's CLIA-certified lab in Vista, California. Exagen charges per test and bills third-party payors including Medicare and commercial insurers. Because AVISE CTD is proprietary and Exagen lacks broad in-network contracts, denial rates are high, and ASP improvement through appeals and payer engagement is the primary financial lever. Exagen also generates a small but growing stream of revenue from pharma and CRO partnerships that use its biomarker assays and sample repository for drug development. Exagen targets further growth through salesforce expansion, continued ASP improvement, and a pipeline that includes lupus nephritis urinary biomarkers and AI-driven disease activity algorithms.