Table 8.8-5. Differential diagnosis of polycythemia vera, secondary erythrocytosis, and relative erythrocytosis

Feature

Polycythemia vera

Secondary erythrocytosis

Relative erythrocytosis

RBC mass

N

WBC count

N or ↑

N

N

Platelet count

N or ↑

N

N

Bone marrow

Trilineage hyperplasia

Erythropoietic lineage hyperplasia

N

Splenomegaly

+++

Pruritus

+/–

SaO2

N

N or ↓

N

Serum vitamin B12 levels

N or ↑

N

N

Granulocyte alkaline phosphatase

N

N

Serum erythropoietin levels

↓ or N

N

Endogenous growth of erythroid colonies

+

↑, increased; ↓, decreased; N, normal; RBC, red blood cell; SaO2, direct measurement of hemoglobin oxygen saturation in arterial blood; WBC, white blood cell.