From the Guidelines
Hemoglobin can increase while hematocrit decreases due to various physiological conditions, laboratory errors, or changes in red blood cell indices. When evaluating this discrepancy, it's essential to consider the potential causes, including dehydration, hemoglobinopathies, macrocytosis, and laboratory errors.
- Dehydration can cause concentrated blood, leading to higher hemoglobin levels, but the hematocrit may be falsely lowered due to red blood cell shrinkage.
- Certain hemoglobinopathies, such as spherocytosis, can result in abnormal red blood cells with higher hemoglobin concentration but reduced volume.
- Macrocytosis, or enlarged red blood cells, can maintain hemoglobin levels while decreasing overall cell volume percentage.
- Laboratory errors, like sample hemolysis, can artificially elevate measured hemoglobin while reducing the apparent cell volume. The study by Auerbach et al. 1 highlights the importance of optimizing iron therapy and correcting underlying factors of persistent anemia, rather than solely relying on ESA therapy, which may not address the root cause of the discrepancy. Key factors to consider when investigating this discrepancy include:
- Examining red blood cell indices
- Reviewing peripheral blood smear results
- Repeating tests to confirm findings and identify the underlying cause
- Assessing for potential laboratory errors or sample handling issues
- Evaluating the patient's clinical context, including hydration status and presence of hemoglobinopathies or other underlying conditions.
From the Research
Hemoglobin and Hematocrit Relationship
- Hemoglobin and hematocrit are two related but distinct measures of red blood cell mass in the body 2.
- Hemoglobin is the protein in red blood cells that carries oxygen, while hematocrit is the proportion of red blood cells in the blood.
- An increase in hemoglobin can occur due to various factors, including increased erythropoiesis (production of red blood cells) stimulated by erythropoietin (EPO) 2, 3.
- On the other hand, a decrease in hematocrit can occur due to factors such as blood loss, hemodilution, or decreased red blood cell production 4, 5.
Possible Explanations for the Discrepancy
- One possible explanation for an increase in hemoglobin with a simultaneous decrease in hematocrit is the presence of a condition that affects red blood cell size or density, such as spherocytosis or thalassemia 6.
- Another possible explanation is the effect of certain medications or substances that can increase hemoglobin levels without affecting hematocrit, such as erythropoiesis-stimulating agents (ESAs) 2, 3.
- Additionally, changes in plasma volume or blood viscosity can also affect hematocrit levels without necessarily affecting hemoglobin levels 4, 5.
Clinical Implications
- The discrepancy between hemoglobin and hematocrit levels can have significant clinical implications, particularly in patients with underlying medical conditions or those receiving certain medications 2, 3, 5.
- It is essential to consider the underlying causes of the discrepancy and to interpret the results in the context of the patient's overall clinical picture 4, 6.
- Further evaluation and monitoring may be necessary to determine the cause of the discrepancy and to guide appropriate management and treatment 2, 3, 5.