Erythropoietin Levels in Patients with Sickle Cell Disease Not in Vaso-Occlusive Crisis

Previous studies of erythropoietin production in sickle cell disease have shown that patients with sickle cell disease generally have an erythropoietin level in the lower end of the expected range. However, this finding was based on a relatively small number of patients including some who were in crisis when the erythropoietin level was drawn. A crisis might affect erythropoietin level by increasing inflammation beyond background and if the patient is transfused, the erythropoietin may not be well correlated with the apparent hemoglobin or hematocrit. In this study, we examine erythropoietin levels in patients with sickle cell disease seen in the outpatient clinic and not in crisis when the level was drawn.

Patients receiving outpatient care at the Thomas Jefferson University Cardeza Sickle Center underwent laboratory evaluation as part of routine standard of care for their disease. Hemoglobin level, creatinine, erythropoietin level, lactate dehydrogenase, and reticulocyte count were extracted anonymously from patient charts for evaluation of erythropoietin in sickle patients in the outpatient setting without crisis and correlation of level with kidney function, hemoglobin level, and ongoing hemolysis.

Forty-eight measurements of erythropoietin from 39 unique patients were extracted. Two were not included as chart review suggested that the patient was in crisis when the values were obtained. Of the remaining 36 patients, three patients had SC disease, four sickle-thalassemia, the rest sickle cell anemia. Three patients received exogenous erythropoietin for hypoplastic anemia or chronic renal failure complicating sickle cell disease. Of the remaining 30 patients, creatinine ranged from 0.2–1.8.

Erythropoietin was higher than the normal range for most patients, as would be expected in a chronic anemia. Erythropoietin level was roughly correlated with hemoglobin, but some patients had erythropoietin levels much lower than expected for their hemoglobin (figure). Erythropoietin was not well correlated with creatinine or with hemolysis. Hemoglobin was higher for patients with SC disease than for sickle cell anemia or sickle-thalassemia, but erythropoietin levels were not significantly different between disease types.

Patients with sickle cell disease who are not in crisis have erythropoietin levels that are elevated, but lower than expected for a healthy patient with chronic anemia, with a greater lack in patients with sickle cell anemia as compared to SC disease. Erythropoietin did not correlate well with kidney function as measured by creatinine or calculated glomerular filtration rate, suggesting that current measures of kidney damage may not be entirely adequate to detect early kidney disease in sickle cell disease.

Figure:

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Hemoglobin (g/dl) versus erythropoietin (mU/ml) in patients with sickle cell disease.

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Hemoglobin (g/dl) versus erythropoietin (mU/ml) in patients with sickle cell disease.

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No relevant conflicts of interest to declare.