CPT code 78399 denotes an unlisted musculoskeletal diagnostic nuclear medicine procedure used when no specific CPT code applies. As an unlisted procedure code, 78399 is important for capturing reimbursement and documentation for novel or uncommon musculoskeletal nuclear medicine studies that fall outside established code sets. Nationally, unlisted codes like 78399 matter because they affect claim adjudication, documentation requirements, and payment variability across payers.

Key payers addressed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical context for musculoskeletal nuclear medicine imaging, the administrative considerations inherent to using an unlisted CPT code, and the typical sites of service where these studies are performed. The publication summarizes benchmarks and policy-relevant topics such as documentation standards, medical necessity justification, and common payer behaviors regarding unlisted nuclear medicine codes.

This summary equips billing, coding, and clinical teams with the essential context for coding and submitting claims with CPT code 78399, clarifies what to expect from payers nationally, and highlights areas where additional documentation or prior authorization may be required. Data not available in the input is noted where relevant.