Role of red cell mass evaluation in patients with MPN and SVT

Patients with splanchnic vein thrombosis (SVT) who may have myeloproliferative neoplasms (MPN) are difficult to diagnose because SVT causes lower blood cell counts which are not typical of MPN diagnosis.¹ Therefore, some patients are categorized as patients with unclassified MPN; therefore, difficult to treat. Here, we summarize a retrospective study by Galtier et al.¹ in Hematologica investigating the role of red blood cell (RBC) mass evaluation in identifying this patient subgroup.

Study design¹

• This study was performed across eight centers in France (N = 71).
• Median age was 44 years and 48% were female.
• The evaluation of RBC mass included endpoints such as:
  • average hemoglobin levels;
  • hematocrit levels;
  • plasma volume value; and
  • erythropoietin levels.
• Splenomegaly and Janus kinase 2 (JAK2)^V617F allele burden were also assessed.

Key findings¹

• Over 50% of patients were diagnosed with masked polycythemia vera (PV) despite reporting normal hemoglobin and hematocrit levels
  • In total, 44% (n = 18) of patients with masked PV and who had a bone marrow biopsy exhibited panmyelosis, a major World Health Organization 2016 criterion for PV
• Overall, 91% of patients with masked PV reported increased plasma volume compared with 46% in patients without PV; suggesting hemodilution could differentiate between masked PV and non-PV.
• During the 77-month follow-up, five patients were initially diagnosed with essential thrombocythemia or MPN-undetermined which progressed to PV diagnosis marked by increased RBC values.
• In patients who were JAK2^V617F positive:
  • Increased RBC mass (>125%) found in 56% of patients and indicated masked PV
  • Decreased RBC mass (<125%) resulted in patients undergoing bone marrow biopsy and diagnosed with MPN-undetermined, primary myelofibrosis or ET

Key learnings

Current treatment guidelines do not recommend cytoreduction for patients with normal hemoglobin, which may result in undertreatment of masked PV within the SVT context. Routine RBC mass evaluation in patients diagnosed with JAK2V617F mutated SVT who have normal RBC values is recommended to detect masked PV. Patients may benefit from accurate diagnosis and treatment with cytoreductive therapy Results from the ongoing France Intergroup of Myeloproliferative Syndromes study (NCT04539678) may further clarify the role of RBC mass in PV diagnosis.