CPT code 88189 covers professional interpretation of flow cytometry studies that evaluate 16 or more markers, typically performed by a pathologist. This code captures a high-complexity diagnostic service used in hematopathology, immunology, and oncology workups where multi-parameter immunophenotyping informs diagnosis, staging, or treatment decisions. Nationally, use of high-parameter flow cytometry has increased as precision diagnostics expand, making accurate coding for interpretation essential for clinical documentation and payer adjudication.

Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an explanation of the clinical context for the code, typical sites of service, and the types of analyses that trigger use of this code. The publication also outlines common modifiers and payer considerations, expected service lines, and related coding items when available. Practical benchmarks and policy updates relevant to laboratory and pathology billing are summarized to help coding and revenue teams understand reimbursement landscapes and documentation expectations.

This summary is for a national audience and focuses on clinical and billing context rather than state-specific rules.