From the Guidelines
Elevated hemoglobin is not synonymous with polycythemia, but rather one potential indicator of the condition, with diagnosis requiring additional criteria such as increased red cell mass, absence of secondary erythrocytosis causes, and presence of specific genetic mutations like JAK2 1.
Key Considerations
- Polycythemia is characterized by an increased concentration of red blood cells, which can include elevated hemoglobin levels, but also requires other diagnostic criteria to be met.
- The 2001 WHO criteria for polycythemia vera include elevated red cell mass, absence of secondary erythrocytosis causes, and presence of specific genetic abnormalities or bone marrow findings 1.
- Proposed revisions to these criteria simplify the diagnosis to include laboratory evidence of increased hemoglobin, hematocrit, or red cell mass, and the presence of a JAK2 mutation, along with minor criteria such as bone marrow histology and serum erythropoietin levels 1.
Diagnostic Approach
- Elevated hemoglobin levels (above 18.5 g/dL in men or 16.5 g/dL in women) can indicate polycythemia, but further evaluation is necessary to confirm the diagnosis and identify the underlying cause.
- This evaluation should include assessment of hematocrit, red blood cell count, and potentially genetic testing for JAK2 mutations if polycythemia vera is suspected 1.
- It's also important to consider temporary elevations in hemoglobin due to dehydration or other factors that do not represent true polycythemia.
Clinical Implications
- Accurate diagnosis of polycythemia is crucial because treatment approaches differ significantly depending on the specific diagnosis and underlying cause.
- For example, polycythemia vera may require phlebotomy, aspirin, or other targeted therapies, while secondary polycythemia may involve addressing the underlying cause of hypoxia or other driving factors 1.
From the Research
Definition of Polycythemia
Elevated hemoglobin can be an indicator of polycythemia, but it is not the only factor to consider. According to 2, an increased hematocrit can be caused by primary proliferative polycythemia, secondary polycythemia, relative polycythemia, or modifications of the red cell mass and plasma volume within their normal ranges.
Diagnostic Criteria
The diagnosis of polycythemia is based on several criteria, including:
- Elevated red blood cell mass 3
- Normal oxygen saturation 3
- Palpable splenomegaly 3
- Elevated hematocrit levels 2, 3
- Elevated hemoglobin levels 4, 3
Distinguishing Between Primary and Secondary Polycythemia
It is essential to distinguish between primary and secondary polycythemia, as the treatment approaches differ. Secondary polycythemia is often caused by underlying non-hematological diseases, such as chronic pulmonary disease or renal disease 4, 3. Primary polycythemia, also known as polycythemia vera, is a chronic myeloproliferative disorder characterized by increased red blood cell mass 5, 3.
Treatment Options
Treatment options for polycythemia include: