From the Guidelines
For a patient with elevated hematocrit, recommended follow-up labs should include a complete blood count (CBC) with peripheral blood smear, serum erythropoietin level, JAK2 V617F mutation testing, and arterial blood gas analysis. According to the most recent and highest quality study 1, these tests are essential in differentiating between primary polycythemia, secondary polycythemia, and relative polycythemia.
Key Tests
- Complete blood count (CBC) with peripheral blood smear: provides baseline values and cell morphology
- Serum erythropoietin level: helps distinguish between primary (low/normal levels) and secondary causes (elevated levels)
- JAK2 V617F mutation testing: identifies mutations associated with myeloproliferative disorders
- Arterial blood gas analysis: helps identify hypoxia-driven erythrocytosis
Additional Tests
- Iron studies (serum iron, ferritin, total iron binding capacity)
- Renal function tests (BUN, creatinine)
- Liver function tests
- Oxygen saturation measurement If polycythemia vera is suspected, bone marrow biopsy and additional genetic testing for CALR and MPL mutations may be necessary 1. These tests help identify underlying conditions that might contribute to erythropoietin production and guide treatment decisions. The study 1 also highlights the importance of measuring P50 (oxygen pressure at 50% hemoglobin-oxygen saturation) in cases where a congenital cause is suspected. However, the more recent study 1 provides a more comprehensive approach to diagnosing and managing elevated hematocrit levels.
From the Research
Follow-up Labs for Elevated Hematocrit
To monitor a patient with elevated hematocrit (high red blood cell count), the following labs are recommended:
- Complete Blood Count (CBC) to monitor hematocrit, hemoglobin, white blood cell count, and platelet count 2, 3, 4, 5
- Blood chemistry tests to monitor liver and kidney function 3
- Leukocyte alkaline phosphatase score to monitor bone marrow activity 3
Frequency of Follow-up Labs
The frequency of follow-up labs depends on the patient's condition and response to treatment. For patients with polycythemia vera, labs should be monitored regularly to assess response to treatment and adjust therapy as needed 2, 4, 5.
- For patients on hydroxyurea, labs should be monitored every 3-6 months to assess response to treatment and adjust dose as needed 2, 5
- For patients undergoing phlebotomy, labs should be monitored regularly to assess the need for continued phlebotomy and adjust frequency as needed 4, 6
Additional Monitoring
In addition to lab tests, patients with elevated hematocrit should be monitored for signs and symptoms of thrombosis, such as chest pain, shortness of breath, and leg swelling 4, 6.