When should I refer out for a hematology consult with erythrocytosis (Elevated Red Blood Cell count)?

From the Guidelines

Referral to a hematologist is warranted for an elevated RBC of 5.7 if accompanied by symptoms such as headaches, dizziness, visual disturbances, or thrombotic events, or if the patient has risk factors for polycythemia vera, such as JAK2 mutation, splenomegaly, or a family history of myeloproliferative disorders. According to the American Society of Hematology 2019 guidelines for immune thrombocytopenia 1, the referring physician should ensure that the patient has follow-up with a hematologist within 24 to 72 hours of diagnosis.

When considering referral, it is essential to evaluate the patient's overall hematologic profile, including hemoglobin and hematocrit levels, as well as the presence of any secondary causes of elevated RBC, such as chronic hypoxic conditions, high altitude living, smoking, dehydration, or inappropriate use of erythropoietin or anabolic steroids. The acc/aha 2008 guidelines for the management of adults with congenital heart disease 1 recommend therapeutic phlebotomy for patients with hemoglobin greater than 20 g per dL and hematocrit greater than 65%, associated with symptoms of hyperviscosity.

Key factors to consider before referral include:

• Significantly increased hemoglobin (>16.5 g/dL in men, >16 g/dL in women)
• Hematocrit >49% in men or >48% in women
• Presence of symptoms such as headaches, dizziness, visual disturbances, or thrombotic events
• Risk factors for polycythemia vera, such as JAK2 mutation, splenomegaly, or a family history of myeloproliferative disorders
• Secondary causes of elevated RBC, including chronic hypoxic conditions, high altitude living, smoking, dehydration, or inappropriate use of erythropoietin or anabolic steroids.

In the absence of these factors, monitoring rather than immediate specialist intervention may be appropriate, as the clinical context and overall hematologic profile are more important than a single laboratory value 1.

From the Research

Hematology Consult for Elevated RBC

• An elevated RBC count of 5.7 may indicate polycythemia vera (PV) or other myeloproliferative neoplasms, and a hematology consult is recommended for further evaluation and diagnosis 2, 3, 4, 5.
• The diagnosis of PV requires the integration of clinical and laboratory findings, bone marrow morphologic features, and JAK2 analysis, and a JAK2 mutation is expected in PV, although its absence does not exclude the diagnosis 4, 5, 6.
• A working diagnosis of PV is considered in the presence of a JAK2 mutation associated with hemoglobin/hematocrit levels of >16.5 g/dL/49% in men or 16 g/dL/48% in women, and morphologic confirmation by bone marrow examination is advised but not mandated 4.
• The presence of splenomegaly, leukocytosis, or thrombocytosis can also support the diagnosis of PV, and a bone marrow examination can help distinguish PV from other myeloproliferative neoplasms 3, 5.
• In cases where the hemoglobin/hematocrit level is diagnostically equivocal, a JAK2 mutation screening and bone marrow morphologic examination can help distinguish PV from essential thrombocythemia (ET) 5.

Referral Criteria

• Patients with an elevated RBC count and suspected PV or other myeloproliferative neoplasms should be referred for a hematology consult for further evaluation and diagnosis 2, 3, 4, 5.
• Referral is particularly recommended for patients with:
  • Hemoglobin/hematocrit levels of >16.5 g/dL/49% in men or 16 g/dL/48% in women 4.
  • Splenomegaly, leukocytosis, or thrombocytosis 3, 5.
  • A family history of myeloproliferative neoplasms 4.
  • A history of thrombosis or other cardiovascular events 4, 5.