From the Guidelines
Polycythemia vera is diagnosed when hemoglobin levels exceed 18.5 g/dL in men or 16.5 g/dL in women, or when hematocrit values are greater than the 99th percentile of the method-specific reference range for age, sex, and altitude of residence, according to the most recent and highest quality study 1. The diagnosis of polycythemia vera (PV) relies on a combination of clinical, laboratory, and molecular findings. Key diagnostic criteria include elevated hemoglobin (Hb) and hematocrit (Hct) levels, as well as the presence of a JAK2 mutation, such as JAK2V617F or exon 12 mutations.
- The significant Hb values for diagnosing PV are:
- 18.5 g/dL in men
- 16.5 g/dL in women
- The significant Hct values for diagnosing PV are:
- Greater than the 99th percentile of the method-specific reference range for age, sex, and altitude of residence
- Hematocrit greater than 99th percentile of method-specific reference range for age, sex, altitude of residence or hemoglobin greater than 17 g/dL in men, 15 g/dL in women if associated with a documented and sustained increase of at least 2 g/dL from an individual’s baseline value that cannot be attributed to correction of iron deficiency, or elevated red cell mass greater than 25% above mean normal predicted value. The management of PV typically involves phlebotomy to maintain hematocrit below 45%, often with cytoreductive therapy like hydroxyurea in high-risk patients, as supported by recent studies 1.
- Phlebotomy is used to reduce blood viscosity and prevent thrombotic complications.
- Cytoreductive therapy, such as hydroxyurea, may be used in high-risk patients to reduce the risk of thrombosis and other complications. It is essential to note that the diagnosis and management of PV require a comprehensive approach, taking into account the patient's overall clinical presentation, laboratory findings, and molecular characteristics.
From the Research
Significant Hb and Hct Values for Diagnosing Polycythemia Vera
The diagnosis of Polycythemia Vera (PV) is characterized by an increased red blood cell mass, which can be indicated by elevated Hemoglobin (Hb) and Hematocrit (Hct) levels. The significant values for these parameters are as follows:
Threshold Values for PV Diagnosis
The World Health Organization (WHO) criteria and the British Committee for Standards in Haematology (BCSH) guidelines provide threshold values for Hb and Hct to diagnose PV. These values are:
- WHO criteria: Hb >16.5 g/dL in men and >16.0 g/dL in women, or Hct >49% in men and >48% in women 5, 4
- BCSH guidelines: Hct >52% in men and >48% in women 5
Importance of Hb and Hct Control
Controlling Hb and Hct levels is crucial in managing PV, as elevated levels can increase the risk of thrombosis. A hematocrit target of less than 45% is recommended to reduce this risk 2, 6. Phlebotomy and cytoreductive therapies, such as hydroxyurea, may be used to achieve this target 2, 6.
Diagnostic Considerations
It is essential to consider clinical and laboratory features associated with myeloproliferative neoplasms (MPN) when evaluating patients with borderline Hb and Hct levels 3. The presence of a JAK2 gene variant can help distinguish PV from secondary causes of erythrocytosis 2.