From the Guidelines
Elevated hemoglobin levels can result from several conditions, including polycythemia vera, living at high altitudes, chronic lung diseases, smoking, certain medications, kidney disorders, heart conditions, and genetic disorders. The causes of elevated hemoglobin levels, also known as polycythemia or hyperhemoglobinemia, are diverse and can be primary or secondary in nature.
Primary Causes
- Polycythemia vera, a bone marrow disorder, is characterized by excessive red blood cell production due to JAK2 gene mutations 1.
- Genetic disorders like congenital polycythemia can cause inherently high hemoglobin levels.
Secondary Causes
- Living at high altitudes triggers increased hemoglobin production as a natural adaptation to lower oxygen levels.
- Chronic lung diseases like COPD reduce oxygen levels, stimulating more red blood cell production.
- Smoking increases carbon monoxide in the blood, reducing oxygen-carrying capacity and prompting hemoglobin production.
- Certain medications, including testosterone, erythropoietin, and anabolic steroids, can boost red blood cell production 1.
- Kidney disorders, particularly renal cell carcinoma, may elevate hemoglobin through erythropoietin release.
- Heart conditions that cause cyanotic heart disease lead to chronically low oxygen levels and compensatory hemoglobin increases. Some key points to consider in the diagnosis and management of elevated hemoglobin levels include:
- A comprehensive evaluation, including blood tests, oxygen saturation measurements, and sometimes bone marrow examination, is necessary to determine the underlying cause.
- Treatment depends on the underlying cause, ranging from phlebotomy for polycythemia vera to smoking cessation, medication adjustments, or addressing primary conditions.
- It is essential to consider the potential risks and consequences of elevated hemoglobin levels, such as increased blood viscosity and thrombosis risk, particularly in the elderly or those with pre-existing vascular disease 1.
From the Research
Causes of Elevated Hemoglobin Levels
Elevated hemoglobin (Hb) levels, also known as polycythemia or hyperhemoglobinemia, can be caused by various factors. The main causes include:
- Primary polycythemia, also known as polycythemia vera (PV), a myeloproliferative neoplasm characterized by an increased red blood cell mass and increased risk of thrombosis 2, 3, 4, 5
- Secondary polycythemia, caused by excess erythropoietin (EPO) or decreased plasma volume 4, 6
- Other factors, such as heavy smoking, chronic pulmonary disease, and renal disease, which can increase red blood cell mass 5
Diagnostic Criteria
The diagnosis of polycythemia vera is made using criteria developed by the Polycythemia Vera Study Group, which include major criteria such as elevated red blood cell mass, normal oxygen saturation, and palpable splenomegaly 5. The World Health Organization (WHO) consensus criteria for diagnosing PV demand the presence of two major criteria and one minor criterion or the presence of the first major criterion and two minor criteria 6.
Laboratory Tests
Laboratory tests, such as serum EPO level and JAK-2 gene mutation test, can help distinguish primary and secondary polycythemia 4, 6. A low EPO level is considered a minor WHO criterion for PV diagnosis, but patients with polycythemia vera can present with a high or low serum EPO level 6.
Clinical Considerations
Polycythemia vera can present with various clinical manifestations, including erythromelalgia, pruritus, splenomegaly, and thrombotic events 2, 3, 4, 5, 6. The condition can also progress to myelofibrosis or acute leukemia 2, 3. Management aims at reducing the hematocrit below 45% to limit thrombo-embolic complications 2, 4.