81270

JAK2 (Janus kinase 2) gene analysis, p.Val617Phe (V617F) variant

CPT code 81270 represents a molecular pathology procedure focused on the identification of the p.Val617Phe (V617F) variant within the Janus kinase 2 (JAK2) gene. The JAK2 gene encodes a non-receptor tyrosine kinase that plays a fundamental role in the JAK-STAT signaling pathway, which regulates the production of blood cells from hematopoietic stem cells. The specific V617F mutation occurs in exon 14, where a valine is replaced by phenylalanine at codon 617. This somatic mutation leads to constitutive activation of the kinase, meaning the signaling pathway is permanently 'turned on,' causing the bone marrow to overproduce myeloid lineage cells. This laboratory test is a critical diagnostic tool in the evaluation of Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). It is most notably associated with Polycythemia Vera (PV), where the mutation is present in nearly 96% of cases, serving as a major diagnostic criterion according to World Health Organization (WHO) standards. Additionally, the mutation is found in approximately 50% to 60% of patients with Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF). The identification of this mutation is vital for distinguishing clonal MPNs from reactive hematopoietic conditions, such as secondary polycythemia or reactive thrombocytosis. The procedure involves genomic DNA extraction, targeted amplification via PCR, and subsequent mutation detection using techniques such as allele-specific PCR, restriction fragment length polymorphism (RFLP) analysis, or sequencing. The quantitative or qualitative result assists hematologists and oncologists in confirming a diagnosis, assessing prognosis, and determining eligibility for targeted therapies such as JAK inhibitors.

Clinical Indications

  • Suspected Polycythemia Vera (PV) based on elevated hemoglobin or hematocrit levels.
  • Suspected Essential Thrombocythemia (ET) based on persistent unexplained thrombocytosis.
  • Evaluation for Primary Myelofibrosis (PMF).
  • Differential diagnosis of erythrocytosis (primary vs. secondary).
  • Investigation of unexplained splenomegaly associated with blood count abnormalities.
  • Evaluation of unusual site venous thrombosis, such as portal vein or hepatic vein (Budd-Chiari syndrome).
  • Monitoring of minimal residual disease in patients with known JAK2-positive MPNs.
  • Clarification of 'triple-negative' MPN status when used in conjunction with CALR and MPL testing.

Procedure Steps

  1. Collection of clinical specimen, typically peripheral blood in an EDTA (purple-top) tube or bone marrow aspirate.
  2. Cell lysis and extraction of genomic DNA (gDNA) from the nucleated cells of the specimen.
  3. Quantification and quality assessment of the extracted DNA to ensure suitability for amplification.
  4. Polymerase Chain Reaction (PCR) amplification of the specific region in exon 14 of the JAK2 gene.
  5. Detection of the V617F variant using specialized techniques (e.g., Allele-Specific PCR, Sanger Sequencing, or High-Resolution Melting Analysis).
  6. Analysis of the resulting data to determine the presence (positive) or absence (negative) of the p.Val617Phe mutation.
  7. Calculation of the variant allele frequency (VAF) if a quantitative assay is performed.
  8. Generation of a laboratory report including the methodology used, clinical interpretation, and reference ranges.

Coding Guidelines

  • 81270 is a Tier 1 Molecular Pathology code and should be used specifically for the p.Val617Phe variant analysis.
  • Do not report 81270 in conjunction with general DNA extraction codes (e.g., 81171-81172) as extraction is inherent to the molecular procedure.
  • If the laboratory performs a broader JAK2 analysis including exons 12-15 or full gene sequencing, refer to CPT 81271 instead of 81270.
  • This code should be reported only once per session, regardless of whether the specimen is peripheral blood or bone marrow.
  • Ensure that the clinical documentation supports medical necessity, such as abnormal CBC results or symptoms of MPN.
  • For reflex testing where multiple genes (JAK2, CALR, MPL) are tested sequentially, each specific Tier 1 code should be reported as the service is performed.

Associated ICD-10 Codes