What are the laboratory findings for Polycythemia (excessive red blood cell count)?

From the Guidelines

Polycythemia is best diagnosed through a comprehensive panel of laboratory tests, including a complete blood count (CBC) with hemoglobin, hematocrit, red blood cell count, white blood cell count, and platelet count, with elevated hemoglobin (>18.5 g/dL in men, >16.5 g/dL in women) and hematocrit being hallmark findings, as per the 2001 WHO criteria 1. The initial workup for polycythemia should include:

• A complete blood count (CBC) with hemoglobin, hematocrit, red blood cell count, white blood cell count, and platelet count
• Erythropoietin (EPO) levels to differentiate between primary and secondary polycythemia
• JAK2 V617F mutation analysis to confirm polycythemia vera
• Arterial blood gas to assess oxygen saturation
• Serum ferritin to rule out iron deficiency masking the condition Key laboratory findings for polycythemia include:
• Elevated red cell mass, hemoglobin, or hematocrit
• Low serum erythropoietin levels
• Presence of JAK2 mutation
• Bone marrow biopsy showing panmyelosis with prominent erythroid and megakaryocytic proliferation
• Thrombocytosis and leukocytosis It is essential to note that the diagnosis of polycythemia vera requires the presence of the first two A-criteria (elevated red cell mass and no cause of secondary erythrocytosis) together with either any other A-criterion or two B-criteria, as per the 2001 WHO criteria 1. Additionally, the presence of JAK2 mutation is a major criterion for the diagnosis of polycythemia vera, as proposed by the revised criteria 1. In clinical practice, a working diagnosis of polycythemia can be made based on disease-characteristic biological and histological features, including serum EPO levels and bone marrow histology, as suggested by the Mayo Clinic Proceedings 1. However, the most recent and highest quality study, published in Blood in 2007, should be prioritized when making a definitive diagnosis 1.

From the Research

Laboratory Findings for Polycythemia

The laboratory findings for polycythemia, specifically polycythemia vera (PV), include:

• Erythrocytosis, characterized by a hemoglobin level greater than 16.5 mg/dL in men or 16.0 mg/dL in women 2
• Leukocytosis (increased white blood cell count) and thrombocytosis (increased platelet count) are common, occurring in 49% and 53% of patients, respectively 2
• Increased red blood cell mass, which is a hallmark of the disease 3
• Presence of a JAK2 gene variant, which is found in more than 95% of patients with PV and helps distinguish it from secondary causes of erythrocytosis 2
• Distinct hemogram results featuring leukocytosis, thrombocytosis, and hypochromic microcytic red blood cells (RBCs) related to associated iron deficiency 4
• Bone marrow biopsy typically shows hypercellularity involving all three cell lines and absent iron stores 3

Diagnostic Criteria

The diagnostic criteria for PV include:

• Erythrocytosis, as evidenced by a high hemoglobin or hematocrit level 2, 4
• Presence of a JAK2 gene variant 2
• Absence of secondary causes of erythrocytosis, such as tobacco smoking or sleep apnea 2
• Presence of other characteristic findings, such as leukocytosis, thrombocytosis, and splenomegaly 2, 3

Laboratory Tests

Laboratory tests used to diagnose and monitor PV include:

• Complete blood count (CBC) to evaluate red blood cell count, white blood cell count, and platelet count 4
• Hemoglobin and hematocrit levels to assess erythrocytosis 2, 4
• JAK2 gene variant testing to confirm the presence of PV 2
• Bone marrow biopsy to evaluate bone marrow hypercellularity and iron stores 3