CPT code 85004 represents an automated differential white blood cell count performed on a blood smear, where a laboratory analyst reviews a slide and an automated system enumerates different white cell types. This test is a routine component of hematology testing used to evaluate infection, inflammation, hematologic disorders, and treatment response; it is widely ordered across hospitals, outpatient laboratories, and clinical settings, making accurate coding and coverage understanding important for national billing consistency.

Key payers included in this analysis are Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise clinical context for the service, standard sites of service, and an overview of payer coverage considerations. The publication outlines common billing practice elements, typical documentation expectations for laboratory differential counts, and operational notes relevant to labs and billing teams.

This summary provides benchmarks for how the service is classified in claims, an explanation of clinical relevance for ordering clinicians and coders, and a policy-oriented overview of payer coverage themes. Data not available in the input includes specific payer rates, associated taxonomies, ICD-10 diagnoses, and related procedure codes; those items are not included here.