CPT 86357 NK Cell Count Reimbursement

CPT code 86357 represents a laboratory immunology test that measures the total count of natural killer (NK) cells in peripheral blood. The test provides objective data on a patient’s innate immune cell population and is used in clinical evaluation of immune status, monitoring of certain immunodeficiencies, and in select specialty care settings. Nationally, utilization of NK cell quantification is relevant to laboratory services, immunology practices, and hospital outpatient diagnostics.

Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context for the test, common sites of service, and the payer landscape relevant to laboratory reimbursement. The publication outlines typical billing practice considerations, common modifier usage (listed separately), and where this code fits within immunology and hematology testing portfolios.

This summary prepares clinicians, laboratory managers, and billing professionals to understand what CPT code 86357 denotes, why it is used clinically, and which major payers typically process claims for NK cell counting. Data not available in the input is noted where applicable in detailed sections.

Billing Code Overview

CPT code 86357 describes a laboratory test that measures the total count of natural killer (NK) cells in a patient’s immune system, typically performed on a blood specimen. This test quantifies NK cells to inform clinical assessment of immune function.

Service type: Laboratory test — immunology/flow cytometry

Typical site of service: Clinical laboratory or hospital outpatient laboratory

Clinical Context

A typical patient is a 42-year-old adult referred by an immunologist or infectious disease specialist for quantification of natural killer (NK) cells after recurrent viral infections, persistent warts, unexplained lymphopenia on complete blood count, or as part of immune evaluation in suspected primary immunodeficiency. The clinician orders the assay to measure total NK cell count from peripheral blood; a phlebotomy appointment is scheduled at an outpatient laboratory or hospital outpatient phlebotomy service. The specimen is collected in anticoagulated whole blood, labeled, and transported to the clinical flow cytometry laboratory. A laboratory technologist performs immunophenotyping using flow cytometry to identify CD16+/CD56+ cells (or equivalent markers) and reports an absolute NK cell count and percentage. Results are reviewed by the ordering clinician to guide diagnosis, immunologic workup, or therapy monitoring (for example, before or after immunomodulatory treatment). Typical sites of service include outpatient hospital laboratory, freestanding clinical laboratory, or tertiary hospital outpatient clinic.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when only the professional interpretation component is billed separately from the technical component.
`TC`

Taxonomy Code	Specialty	Notes
207Q00000X	Clinical Pathology	Pathologists oversee laboratory testing and interpretation.
207L00000X	Hematology & Hematopathology	Hematopathologists interpret immune cell quantification and peripheral blood immunophenotyping.
207K00000X	Allergy & Immunology	Allergists/immunologists order and interpret NK cell testing for immune deficiency evaluation.
208000000X	Infectious Disease	Infectious disease specialists order testing for recurrent or severe viral infections.
207P00000X	Clinical Laboratory	Clinical laboratory scientists/technologists perform the assay and reporting.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`D80.9`	Immunodeficiency, unspecified	NK cell enumeration may be performed during evaluation for suspected primary or secondary immunodeficiency.
`D72.829`	Other abnormality of white blood cells, unspecified	Abnormal lymphocyte counts prompt subset testing including NK cells.
`B27.9`	Infectious mononucleosis, unspecified	Viral infections can be associated with changes in NK cell numbers and trigger testing.
`B05.9`	Measles without complication	Severe or unusual viral infections may prompt immune evaluation including NK cell count.
`R53.83`	Other fatigue	Non-specific systemic symptoms like persistent fatigue may lead to immune evaluation, including NK cell testing.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`36415`	Collection of venous blood by venipuncture	Performed immediately before the NK cell assay to obtain the specimen.
`88360`	Immunohistochemistry, per specimen; initial single antibody stain	Occasionally used in specialized labs for tissue-based NK marker studies when biopsy immunophenotyping is required.
`86356`	Immunohematology testing (example: testing for cell markers) — note: related immunologic assays	Performed in parallel when broader lymphocyte subset panels or functional assays are ordered.
`86361`	Antibody testing (e.g., natural killer cell function assays)	Performed when functional NK cell assays are ordered in addition to enumeration.
`87220`	Culture, bacterial (for other concurrent infectious workup)	May be performed concurrently when infection is suspected and cultures are indicated.

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Summary & Overview

CPT 86357: Natural Killer (NK) Cell Count