Summary & Overview
CPT 81338: MPL Gene Variant Analysis for Myeloproliferative Neoplasms
CPT code 81338 represents a targeted molecular diagnostic assay for detection of common MPL gene variants (for example, W515A/K/L/R) that can be associated with myeloproliferative neoplasms such as essential thrombocythemia, particularly in patients negative for JAK2 V617F. This code captures the technical laboratory testing performed on blood or other specimens to identify specific MPL sequence variants and supports diagnostic and prognostic evaluation in hematology-oncology practice. Nationally, molecular testing for MPN-related mutations is an important component of precision diagnostics and care pathways for suspected myeloproliferative disorders.
Key payers covered in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise clinical context for when the test is used, the typical laboratory setting, and what the code represents in billing workflows. The publication outlines payer coverage considerations and common modifiers encountered, summarizes the clinical relevance for hematology practices, and indicates where input data are not available. This resource is intended to help coding managers, laboratory directors, and revenue teams understand the role of CPT code 81338 within molecular diagnostics for MPNs and what to expect from national payers in coverage and claims processing.
Billing Code Overview
CPT code 81338 describes a molecular diagnostic laboratory test that detects common variants in the MPL (MPL proto–oncogene, thrombopoietin receptor) gene, including variants such as W515A, W515K, W515L, and W515R. These variants may be associated with myeloproliferative neoplasms (MPN), including essential thrombocythemia (ET), particularly in patients who are negative for the JAK2 V617F mutation.
Service Type: Molecular pathology / targeted gene variant analysis
Typical Site of Service: Clinical laboratory or hospital laboratory (blood specimen analysis)
Data not available in the input for Associated Taxonomies, ICD-10 Diagnoses, Related Codes, and Service Line.
Clinical & Coding Specifications
Clinical Context
A 58-year-old patient presents to a hematology clinic with sustained thrombocytosis on routine labs and symptoms of headache and erythromelalgia. Prior testing for JAK2 V617F is negative. The hematologist orders a targeted molecular assay for common activating variants in the MPL gene (for example W515A/K/L/R) to evaluate for a myeloproliferative neoplasm such as essential thrombocythemia. The specimen is a peripheral blood draw obtained in the outpatient phlebotomy unit and sent to the molecular diagnostics laboratory. In the laboratory workflow, a molecular technologist performs DNA extraction, PCR or targeted sequencing, and variant analysis; the laboratory analyst documents results and the pathologist reviews and signs out the report. Typical site of service is outpatient ambulatory clinic or independent/ hospital-based clinical laboratory performing high-complexity molecular testing. Billing occurs under the laboratory technical component for the assay when performed by the lab; a professional component modifier may apply when a pathologist signs out and bills separately.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When a physician/pathologist bills for interpretation/reporting separate from the lab technical work |