Hematocrit – Hematocrit – The hematocrit (HCT) is expressed as the percent of a blood sample occupied by intact RBC. Polycythemia in the adult patient is considered to be present when the HCT is !" or #$ percent in women and men% respecti&ely. ' Hemoglobin concentration – concentration – The hemolobin concentration (HB) is expressed in rams per *++ m, of whole blood or in rams per liter lite r of whole blood. Polycythemia in the adult is considered to be present when the HB is *-.# or *".# d,% or *-# or *"# , in women and men% respecti&ely. ' Red blood cell count – count – The red blood cell (RBC) count is expressed as the number of RBC per micro, or liter of whole blood. The normal RBC count is approximately # x *+ - cells per micro, or # x *+ *$ cells per ,. /t is the least often used of the three tests to suest polycythemia% since patients with thalassemia minor may ha&e an ele&ated RBC count% but a reduced HCT or HB due to the presence of an increased number of small (microcytic)% poorly hemolobini0ed (hypochromic) red cells.
TERMINOLOGY 1 TERMINOLOGY 1 The three measurements listed abo&e (red blood cell 2RBC3 count% hemolobin 2HB3% and hematocrit 2HCT3) are concentrations and therefore dependent upon the plasma &olume as well as the RBC mass (RC4). Relative polycythemia 1 polycythemia 1 5n isolated decrease in plasma &olume can ele&ate the HB% HCT% and RBC count. The state of chronically reduced red uced plasma &olume &olum e with ele&ated HB or HCT has been called aisboc67s disease% spurious polycythemia% stress erythrocytosis% apparent polycythemia% and pseudopolycythemia% pseudopolycythemia% althouh many may be examples of smo6ers7 polycythemia Abolute polycythemia 1 polycythemia 1 /n absolute polycythemia (erythrocytosis) there is an increased RC4. Patients are further cateori0ed into primary and secondary forms !rimary polycythemia 1 polycythemia 1 Primary polycythemia is caused by an ac8uired or inherited mutation leadin to an abnormality within RBC proenitors9 it includes polycythemia &era (P:) and rare familial &ariants (e% acti&atin mutations of the erythropoietin receptor% Chu&ash polycythemia /diopathic erythrocytosis has been used to cateori0e patients with primary
polycythemia who do not fulfill con&entional criteria for the dianosis of P: 2;3% includin neati&ity for the exon *! and exon *$ <5=$ mutations "econdary polycythemia 1 >econdary polycythemia is caused by a circulatin factor stimulatin erythropoiesis% usually erythropoietin (?po). /t is most often due to an ?po response to hypoxia% but can also result from an ?po@secretin tumor. #ombined polycythemia 1 Patients may ha&e an increased RC4 as well as a reduced plasma &olume% a combination most commonly seen in smo6ers (ie% Asmo6ers7 polycythemiaA) Inapparent polycythemia 1 /f the RC4 and plasma &olume are e8ually increased% HB% HCT% and RBC count remain normal .Polycythemia can only be detected &ia blood &olume studies.
>e&eral basic steps towards this e&aluation are described below 25t a minimum% the followin should be obtained in all patients 'History and physical examination 'Pulse oximetry andor arterial oxyen saturation at rest and after exercise 'Complete blood count 'rinalysis ',i&er function studies 'Chest x@ray >ymptoms due to the underlying polycythemia are related to the increased &iscosity of blood (hyper&iscosity) and may include any or all of the followin chest and abdominal pain% myalia and wea6ness% fatiue% headache% blurred &ision% transient loss of &ision% paresthesias% slow mentation andor a sense of depersonali0ation. ' >ymptoms suestin the presence of underlying pulmonary dieae include shortness of breath% dyspnea on exertion% chronic couh% history of cyanosis% and hypersomnolence with unintentional sleep. ' >ymptoms suestin the dianosis of polycythemia vera $!%& include post@ bath pruritus% erythromelalia% out% arterial or &enous thromboses% hemorrhae% and early satiety due to the presence of splenomealy.
5ccordin to $++" re&ised Dorld Health Erani0ation (DHE) uidelines% dianosis of P: re8uires the presence of both maFor criteria and one minor criterion or the presence of the first maFor criterion toether with two minor criteria.
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4aFor DHE criteria are as follows Hemolobin *".# d, in men and *-.# d, in women% or other e&idence of increased red blood cell &olume Presence of <5=$-*;: G or other functionally similar mutation% such as JAK2 exon *$ mutation4inor DHE criteria are as follows >ee the list below Bone marrow biopsy showin hypercellularity for ae with trilineae rowth (panmyelosis) with prominent erythroid% ranulocytic% and mea6aryocytic proliferation >erum erythropoietin le&el below the reference rane for normal ?ndoenous erythroid colony formation in &itro.
