CPT code 86039 denotes the technical laboratory assay to determine the titer of antinuclear antibodies (ANAs) in serum. ANA testing is a foundational diagnostic tool in the workup of suspected autoimmune diseases such as systemic lupus erythematosus and other connective tissue disorders, making this code clinically relevant across inpatient and outpatient laboratory settings nationwide. Payers commonly involved in coverage and claims for this service include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. This publication provides a concise national overview of CPT code 86039, explaining its clinical purpose, typical sites of service, and the payer landscape. Readers will find benchmark context for utilization and billing practice, summaries of common modifiers and service-line considerations, and clinical context to inform coding and documentation alignment. Data not available in the input will be noted where applicable. The content is intended to clarify what CPT code 86039 represents, where the service is performed, and what topics are relevant for payers and billing staff when processing ANA titer technical component claims.