Is an isolated elevated Red Blood Cell (RBC) count with normal hemoglobin and hematocrit significant?

From the Guidelines

Isolated elevated red blood cell (RBC) count with normal hemoglobin and hematocrit is generally not clinically significant. This finding often represents a relative polycythemia, which can occur due to dehydration, smoking, or living at high altitude 1. The normal hemoglobin and hematocrit values suggest that oxygen-carrying capacity is adequate, which is the primary clinical concern with red blood cell abnormalities. No specific treatment is typically needed for this isolated finding, but addressing underlying causes like dehydration or smoking cessation may be beneficial.

Key Considerations

• Relative polycythemia can be caused by various factors, including dehydration, smoking, or high altitude, and does not necessarily indicate a pathological condition 1.
• The presence of a normal hemoglobin and hematocrit level indicates that the oxygen-carrying capacity of the blood is within normal limits.
• Absolute polycythemia, such as polycythemia vera, typically shows elevations in all three parameters (RBC count, hemoglobin, and hematocrit) and requires medical intervention.

Diagnostic Approach

• If an isolated elevated RBC count is found, it is essential to ensure the patient is well-hydrated before repeat testing.
• A diagnostic algorithm, including the determination of serum EPO and examination of bone marrow histology, can be used to diagnose polycythemia vera, but this is typically not necessary for isolated elevated RBC count with normal hemoglobin and hematocrit 1.
• The measurement of RCM is seldom required, and a normal-range RCM reading does not rule out the possibility of polycythemia vera.

Management

• No specific treatment is typically needed for an isolated elevated RBC count with normal hemoglobin and hematocrit.
• Addressing underlying causes, such as dehydration or smoking cessation, may be beneficial.
• Repeat testing in 3 months may be sufficient if the diagnostic possibility of polycythemia vera is not entertained 1.

From the Research

Isolated Elevated RBC with Normal Hemoglobin and Hematocrit

• Isolated elevated red blood cell (RBC) count with normal hemoglobin and hematocrit levels can be significant in certain contexts 2, 3.
• An absolute erythrocytosis is present when the red cell mass is greater than 125% of the predicted, which is suspected when the hemoglobin or hematocrit is above the normal range 2.
• However, in cases where hemoglobin and hematocrit are within normal ranges, the significance of isolated elevated RBC count may depend on other factors, such as the presence of underlying conditions like chronic kidney disease (CKD) 3, 4, 5.
• In patients with CKD, erythrocytosis can occur due to various causes, including cystic kidney diseases, kidney or other erythropoietin-secreting neoplasms, and high-altitude renal syndrome 3.
• The interpretation of erythropoietin levels in patients with various degrees of renal insufficiency and anemia can provide valuable insights into the underlying causes of erythrocytosis 4, 5.
• A significant inverse correlation between erythropoietin and hemoglobin levels was observed in patients with creatinine clearance above 40 mL/min, indicating that hemoglobin negatively regulates erythropoietin above this cut-off 4.
• In patients with CKD, glomerular filtration rate (GFR) positively correlated with hemoglobin and erythropoietin, while the correlation between GFR and serum creatinine was negative 5.