From the Guidelines
The workup of elevated hemoglobin and hematocrit in primary care should begin with confirming the elevation through repeat testing, as dehydration can cause transient increases, and then evaluate for secondary causes and consider therapeutic phlebotomy for symptomatic patients or those with significantly elevated levels. The initial step in evaluating elevated hemoglobin and hematocrit is to confirm the elevation through repeat testing, as dehydration can cause transient increases 1. Once confirmed, a thorough history and physical examination should be performed to evaluate for secondary causes including smoking, chronic lung disease, high altitude exposure, and sleep apnea. Additional laboratory tests should be ordered, including:
- Serum erythropoietin levels
- JAK2 mutation analysis
- Complete blood count with peripheral smear
- Comprehensive metabolic panel
- Arterial blood gases if hypoxemia is suspected Consider abdominal ultrasound to evaluate for hepatomegaly or splenomegaly. If secondary causes are ruled out, refer to hematology to evaluate for polycythemia vera or other myeloproliferative disorders. While awaiting diagnosis, recommend smoking cessation if applicable, adequate hydration, and avoidance of iron supplements unless iron deficiency is confirmed. Therapeutic phlebotomy may be considered for symptomatic patients or those with significantly elevated levels (hematocrit >65%) to reduce blood viscosity and associated thrombotic risks, as indicated by the acc/aha 2008 guidelines 1. The urgency of workup depends on the degree of elevation, associated symptoms, and risk factors for complications.
From the Research
Workup of Elevated Hemoglobin and Hematocrit
The workup of elevated hemoglobin and hematocrit in the primary care setting involves a step-by-step approach to diagnose and interpret the most common blood disorders.
- A complete blood cell count (CBC) with differential count and reticulocyte count is essential to narrow the differential diagnosis and tailor the subsequent evaluation 2.
- The interpretation of CBC results requires practice, and every clinician can learn to identify possible diagnoses before consulting a specialist 2.
- The components of the CBC include the red blood cell count, hemoglobin, hematocrit, red blood cell indices, reticulocyte count, white blood cell count and differential, and platelet count 3.
Diagnostic Criteria for Polycythemia Vera
Polycythemia vera (PV) is a primary acquired erythrocytosis, and its diagnosis involves a combination of major and minor diagnostic criteria.
- The Polycythemia Vera Study Group (PVSG) used a combination of major and minor diagnostic criteria, but these guidelines have some limitations 4.
- Absolute erythrocytosis can be assumed in males and females with packed cell volume (PCV) values greater than 0.60 and greater than 0.56, respectively 4.
- A satisfactory strategy of investigation for a secondary erythrocytosis must be used, and hypoxemia, as well as renal and hepatic pathology, must be excluded 4.
Initial Evaluation and Treatment
The initial evaluation and treatment of PV involve careful interpretation of hematocrit values, red cell count, and red cell mass when available, and bone marrow histomorphology to distinguish PV from other JAK2V617F myeloproliferative neoplasms (MPNs) 5.
- Phlebotomy (PHL) is often used as an initial treatment, but it may be inadequate in the long term, and cytoreduction is needed for most patients 5.
- Cytoreductive therapy using interferon-alpha or hydroxyurea is an alternative strategy, and interferon is the preferred first-line agent due to improved survival outcomes 5.