A more contemporary approach to the diagnosis of PV is outlined in Table 47.5. It includes the demonstration of an increased RBC mass, particularly for
(a) Increased RBC mass or Hct >60% in men, 58% in women
(b) Absence of any cause of secondary erythrocytosis or familial polycythemia (assumes serum eythro poietin level not increased)
And any three of the following:
(c) Palpable splenomegaly
(d) serum erythropoietin <5U/mL
(g) Bone marrow biopsy
(i) Cellularity, reticulin, fibrosis
(ii) Megakaryocyte abnormalities
* Please see text regarding JAK2 expression patients with only a modest increase in hematocrit. It is not possible to predict an increased RBC mass from a single hematocrit value, except for a hematocrit more than 60% in men and 58% in women. A careful history, physical examination, and screening laboratory studies, including oxygen saturation values, should exclude polycythemia due to inadequate oxygen delivery to tissues with respect to need; a serum erythropoietin value should be elevated in those cases where the polycythemia is associated with a benign or malignant tumor. As always, an accurate history is important. It should exclude familial poly-cythemias.
A proactive approach to the diagnosis of PV is shown in Table 47.5. Splenomegaly occurs in about 60% of patients, an elevated WBC in 60%, increased platelets in 75%. In PV, the serum erythropoietin most often, but not always, is less than 5U/mL. A bone marrow biopsy is helpful, both for establishing the diagnosis and for baseline purposes in order to follow the progress of the disease. Due attention should be paid to cellularity (panhyperplasia), iron stores (which should be diminished or absent), reticulin content and fibrosis, and abnormal megakaryocyte morphology.
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