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Erythropoietin 1337

○ Appropriate increase in erythropoietin production of erythropoietin reported rarely dachshunds), have a higher upper limit
occurs secondary to hypoxemia. with renal lymphoma, renal and hepatocel- of the reference interval for hematocrit.
VetBooks.ir etin occurs uncommonly from hypoxia Next Diagnostic Steps to Consider Specimen Collection and Handling
See p. 1351.
○ Inappropriate production of erythropoi-
lular carcinoma, and nasal fibrosarcoma;
polycythemia vera. See p. 1222.
restricted to kidneys (e.g., right-to-left
shunting patent ductus arteriosus [PDA])
or, rarely, paraneoplastic expression of if Levels Are High EDTA whole blood (lavender top tube)
erythropoietin). Verify instrument hematocrit with manual Pearls
○ Polycythemia vera (p. 806) is a chronic test (packed cell volume). After ruling out the • “Polycythemia” has commonly, but
myeloproliferative disease resulting from more common causes of relative erythrocytosis incorrectly, been used for describing the
clonal proliferation of well-differentiated (e.g., physical exam and evaluation of serum condition of increased red blood cell mass;
erythrocytes without an increase in basal albumin concentration for dehydration), “erythrocytosis” is the correct term, whereas
levels of erythropoietin. consider arterial PO 2 measurement or SpO 2 , “polycythemia” describes the state in which
• Marked erythrocytosis, especially with abso- urinalysis and abdominal ultrasound (evaluate all blood cell lines are increased.
lute erythrocytosis, can cause hyperviscosity kidneys), chest radiographs, echocardiography, • Hypovolemia/dehydration is the most
and resultant tissue hypoxia and thrombosis. +/− erythropoietin assay. common cause of erythrocytosis in dogs
and cats.
Causes of Abnormally High Levels Important Interspecies Differences
• Relative: dehydration; splenic contraction • Erythrocytosis caused by epinephrine- AUTHOR: Stephen D. Gaunt, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
• Absolute: high altitude; most right-to-left induced splenic contraction is more likely
cardiac shunts; chronic pulmonary diseases; in cats.
renal hypoxia due to right-to-left shunt- • Certain breeds of dogs, especially sighthounds
ing PDA or renal tumor; paraneoplastic (e.g., greyhounds) and some others (e.g.,

Erythropoietin

Definition renal cyst, pyelonephritis, or hydronephrosis; Lab Artifacts
Renal hormone that stimulates erythropoiesis hyperthyroidism; EPO therapy. Regardless of Increased: hemolyzed or lipemic specimens
in the bone marrow in response to tissue cause, secondary erythrocytosis is the result.
hypoxia Specimen Collection and Handling
Next Diagnostic Steps to Consider Serum (red top tube) or heparinized plasma
Synonym if Levels Are High (green top tube); separate serum or plasma from
EPO • Confirm erythrocytosis. If absent, EPO result erythrocytes, freeze, and transport frozen. Do Laboratory Tests
may be spurious or represent early disease. not use serum separator tubes.
Physiology Serial monitoring of hematocrit is warranted
EPO is produced primarily by the kidney (sole in these cases. Relative Cost: $$$
source in dogs), with small amounts produced • Identify cause of any hypoxemia-inducing
by the liver in some species. Tissue hypoxia condition: arterial blood gas measurement, Pearls
stimulates EPO production. EPO induces thoracic imaging, possibly echocardiography • Measurement of serum EPO levels is an
differentiation of erythroid progenitor cells to • Evaluate for neoplasia, kidney lesions, and appropriate test in patients with repeatable
rubriblasts, stimulates mitosis of erythroid cells, endocrinopathy. absolute erythrocytosis without hypoxemia.
reduces maturation time, and accelerates bone • “Polycythemia” refers to increase in all
marrow release of reticulocytes. Causes of Abnormally Low Levels circulating cell lines but is often used for
Decreased EPO in the presence of erythrocytosis referring to erythrocytosis, an increase in
Reference Interval and normal PaO 2 suggests polycythemia vera; circulating red blood cells.
Radioimmunoassay method: dogs, 8.4-28 mU/ although measurement of EPO is not clini-
mL; cats, 10-30 mU/mL cally indicated in anemia, low EPO would be AUTHOR: Fidelia R. Fernandez, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
expected with chronic kidney disease–associated
Causes of Abnormally High Levels anemia.
Hypoxemia-inducing cardiovascular or
pulmonary disease; hypoxemia due to high Next Diagnostic Steps to Consider
altitude; inappropriate EPO production due if Levels Are Low
to EPO-producing neoplasm (leiomyoma, Assess renal structure (diagnostic imaging) and
leiomyosarcoma, renal carcinoma, others), function.

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