Adult recommended minimum: 1.0 mL serum Adult/Pediatric absolute minimum: 0.5 mL serum If additional tests are going to be ordered, extra red top tubes may be needed. Please call the lab for consultation.

Normal serum concentrations of erythropoietin for 95% of individuals with normal hematocrits range from 4-27 mU/mL. As the hematocrit is lowered by iron deficiency, aplastic or hemolytic anemia, the concentration of erythropoietin increases as shown in the graph below. In the absence of anemia, elevated concentrations are seen in renal tumors, as a manifestation of renal transplant rejection, and in secondary polycythemia. Low values may be observed in hemochromatosis. Decreased erythropoietin concentrations with an elevated hematocrit are observed in patients with polycythemia rubra vera, and with a decreased hematocrit in patients with HIV infection who are receiving AZT. Patients on AZT who have anemia and erythropoietin concentrations of less than or equal to 500 mU/mL, may benefit from therapy with recombinant EPO (NEJM 322:1488-1493, 1990). EXPECTED ERYTHROPOIETIN CONCENTRATIONS IN PATIENTS WITH UNCOMPLICATED ANEMIA ERYTHROPOIETIN (mU/mL) 100,000| | | | 10,000|............. | ............. | ............. | ............. 1,000| ............. | ............. | ............. | ............. 100| ............. | ............. | ............. 10| ............. | ............. |______________________________________________ 10 20 30 40 50 60 70 (HEMATOCRIT %) Source: Caro J and Erslev AJ. Erythropoietin assays and their use in the study of anemias. Contrib Nephrol 1988; 66:54-62. Review.

Erythropoietin (EPO), a glycoprotein produced primarily by the kidney, is the factor regulating red blood cell (RBC) production in mammals. Renal production of EPO is regulated by changes in oxygen availability. Under conditions of hypoxia, the level of EPO in the circulation increases, leading to increased production of RBCs. The overproduction of EPO may be associated with certain pathophysiological conditions. Polycythemia exists when there is an overproduction of RBCs. Primary polycythemias, such as polycythemia vera, are caused by EPO-independent growth of erythrocytic progenitors from abnormal stem cells. Low-to-normal levels of EPO are found in the serum of affected patients. Various types of secondary polycythemias are associated with the production of higher than normal levels of EPO. The overproduction of EPO may be an adaptive response associated with conditions that produce tissue hypoxia, such as living at high altitude, chronic obstructive pulmonary disease, cyanotic heart disease, sleep apnea, high-affinity hemoglobinopathy, smoking, or localized renal hypoxia. In other instances, excessive EPO levels are the result of production by neoplastic cells. Cases of increased EPO production and erythrocytosis have been reported for patients with renal carcinomas, benign renal tumors, Wilms' tumors, hepatomas, liver carcinomas, cerebellar hemangioblastomas, adrenal gland tumors, smooth muscle tumors, and leiomyomas. Deficient levels of EPO production are found in conjunction with certain forms of anemias. These include anemia of renal failure and end-stage renal disease, anemias of chronic disorders, chronic infections, autoimmune diseases, rheumatoid arthritis, AIDS, malignancies, anemia of prematurity, anemia of hypothyroidism, and anemia of malnutrition. Many of these conditions are associated with the generation of interleukin 1 (IL-1) and tumor necrosis factor (TNF- alpha), factors that have been shown to be inhibitors of EPO activity. AIDS patients suffering from zidovudine-induced anemia have been reported to benefit from treatment with recombinant human erythropoietin if the baseline erythropoietin level is is less than or equal to 500 mU/mL. Normal serum concentrations of erythropoietin for 95 percent of individuals with normal hematocrits range from 4-27 mU/mL. As the hematocrit is lowered by iron deficiency, aplastic, or hemolytic anemia, the concentration of erythropoietin increases as shown in the diagram above. In the absence of anemia, elevated concentrations are seen in renal tumors as a manifestation of renal transplant rejection and in secondary polycythemia. Low values may be observed in hemochromatosis. Deceased erythropoietin concentrations with an elevated hematocrit are observed in patients with polycythemia rubra vera and with a decreased hematocrit in patients with HIV infection who are receiving AZT. Patients on AZT who have anemia and erythropoietin concentrations of less than or equal to 500 mU/mL may benefit from therapy with recombinant EPO. Other forms of anemias are EPO-independent and affected individuals will show elevated levels of EPO. These include aplastic anemias, iron deficiency anemias, thalassemias, megaloblastic anemias, pure red-cell aplasias, and myelodysplastic syndromes. Patients suffering from uncomplicated, EPO-independent anemia will have elevated concentrations of erythropoietin that are appropriate for the level of anemia. These values fall within the shaded area of the diagram above. Patients suffering from EPO-deficient anemias have erythropoietin levels that are inappropriately low for the degree of anemia. These values fall below the shaded area of the diagram above.