Summary & Overview
CPT 85540: Leukocyte Alkaline Phosphatase and White Blood Cell Count
CPT code 85540 represents a laboratory diagnostic procedure that measures leukocyte alkaline phosphatase (LAP) activity and includes a white blood cell count. This hematology assay supports evaluation of neutrophil function and overall white blood cell levels, informing diagnosis and monitoring of hematologic disorders nationally. The code is relevant to hospitals, independent clinical laboratories, and reference labs that perform blood-based diagnostic services.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for the test, typical sites of service, and the kinds of billing and coverage considerations commonly associated with lab-based hematology codes. The publication outlines benchmarks and payment policy context where available, summarizes common modifier usage provided in the input, and highlights areas where input data was not provided.
This summary is intended to provide clinicians, coding professionals, and policy analysts with a concise reference to the clinical purpose of CPT code 85540, the payer landscape addressed, and the types of operational and policy topics discussed in the full publication.
Billing Code Overview
CPT code 85540 describes a laboratory procedure in which a laboratory analyst measures leukocyte alkaline phosphatase (LAP) levels and performs a white blood cell count on a blood specimen. This test evaluates neutrophil enzyme activity and white blood cell quantity to aid clinical assessment of hematologic conditions.
-
Service type: Laboratory diagnostic test
-
Typical site of service: Clinical laboratory or hospital laboratory
Clinical & Coding Specifications
Clinical Context
A 58-year-old outpatient with leukocytosis and a history of chronic myeloproliferative disorder presents for hematology evaluation. The clinician orders a leukocyte alkaline phosphatase (LAP) score and manual white blood cell differential to help differentiate reactive neutrophilia from a myeloproliferative neoplasm such as polycythemia vera or chronic myelogenous leukemia (CML). Blood is drawn in the clinic or outpatient lab; a phlebotomist labels and sends the EDTA-anticoagulated specimen to the clinical laboratory. A medical laboratory scientist performs a peripheral blood smear, counts leukocytes, and performs the LAP staining and scoring. Results are transcribed into the laboratory information system and reported to the ordering hematologist for correlation with clinical findings and molecular testing (for example, BCR-ABL testing). Typical site of service: hospital outpatient laboratory or independent clinical laboratory; specimen collection may occur in an office, outpatient phlebotomy draw station, or inpatient setting if ordered during hospitalization.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
00 | Default/No modifier | Use when no specific modifier applies |
11 | Office or Other Outpatient Visit |