Erythrocytosis refers to an abnormally high concentration of red blood cells in the blood, indicated by elevated hemoglobin and/or hematocrit levels. While red blood cells are necessary for transporting oxygen, an excess can lead to increased blood thickness and health complications. An erythrocytosis workup determines the underlying reason for this elevated count and identifies its specific type, guiding management strategies.
Recognizing Erythrocytosis
Individuals with erythrocytosis may experience common, non-specific symptoms like headaches, dizziness, general fatigue, and shortness of breath. Some people might also notice blurred vision or persistent itching.
Often, erythrocytosis is detected incidentally during routine blood tests, even before noticeable symptoms appear. It is important to distinguish between “absolute erythrocytosis,” a true increase in red blood cells, and “relative erythrocytosis,” where the count appears high due to reduced plasma volume, such as from dehydration. The workup aims to differentiate between these possibilities.
First Steps in Evaluation
The initial assessment for erythrocytosis begins with a thorough medical history. The doctor will inquire about factors such as smoking habits, current medications, recent travel, and any family history of blood disorders. Symptoms that might suggest sleep apnea, like snoring or daytime sleepiness, are also explored.
Following the medical history, a comprehensive physical examination is performed. This involves checking for signs like an enlarged spleen, which can be indicative of certain bone marrow disorders. The examination also assesses for high blood pressure or signs of dehydration, which could point towards relative erythrocytosis. These early steps help guide subsequent laboratory and advanced testing, assisting in the differentiation between apparent and true erythrocytosis.
Laboratory and Advanced Testing
The complete blood count (CBC) is a fundamental initial blood test in an erythrocytosis workup. This test provides information on hemoglobin, hematocrit, and red blood cell count, which are direct indicators. A peripheral blood smear may also be examined under a microscope to check for abnormally shaped or sized cells, which can suggest a myeloproliferative neoplasm.
Measuring erythropoietin (EPO) levels in the blood is another important step. EPO is a hormone that stimulates red blood cell production, and its levels help differentiate between primary and secondary erythrocytosis. Low EPO levels typically suggest a primary cause, while high EPO levels are often seen in secondary erythrocytosis. Oxygen saturation measurements assess the amount of oxygen in the blood, helping to identify chronic hypoxia as a potential cause.
Genetic testing is frequently performed, particularly for the JAK2 V617F mutation, a common marker for Polycythemia Vera. Other mutations (e.g., JAK2 exon 12, VHL, EPAS1) may also be tested depending on the initial findings. A bone marrow biopsy might be necessary to confirm diagnoses like Polycythemia Vera or other myeloproliferative neoplasms if other tests are inconclusive.
Pinpointing the Cause
Once the results from the initial clinical assessment and laboratory tests are gathered, the underlying cause of erythrocytosis can often be identified. Primary erythrocytosis originates from an issue within the bone marrow itself, with Polycythemia Vera being a common example. This type is often characterized by an elevated red blood cell count, typically accompanied by low erythropoietin levels and a positive JAK2 V617F mutation. In these cases, other blood cell lines, such as white blood cells and platelets, may also be elevated.
Secondary erythrocytosis results from an external factor stimulating red blood cell production. Common causes include chronic hypoxia, which can arise from conditions like sleep apnea, lung disease, or prolonged exposure to high altitudes. Certain kidney diseases or tumors can also lead to secondary erythrocytosis by producing excess erythropoietin. High erythropoietin levels often accompany these conditions.
Apparent erythrocytosis (relative erythrocytosis) is not a true increase in red blood cells but rather a reduction in plasma volume, making the red blood cell concentration appear higher. This can occur due to dehydration, severe burns, or even as a reversible effect of cigarette smoking due to elevated carboxyhemoglobin levels. The workup helps to distinguish these different categories, guiding the appropriate next steps in patient care.