Polycythemia vera diagnosis
Your doctor will perform a full physical examination with special emphasis on signs of blood disorders. A peculiar feature of polycythemia is a red plethoric face, this is owing to the increase in red cell count. This can also be noticed in the nails. Since the blood is thick and viscid, patients usually have hypertension. Other signs of blood clotting disorders can be seen including bruises and small red dots of the skin due to bleeding into the skin layers.
A) Laboratory investigations:
In all blood disorders, complete blood count constitutes the main laboratory investigation ordered, and PV is no exception. However, estimation of hemoglobin level or red cell count may be inaccurate since it is highly dependent on the plasma volume. For example: if there is severe dehydration or any other cause for loss of plasma fluids, the level of hemoglobin will be relatively increased and the same happens with blood viscosity. To overcome that obstacle, doctors use red cell mass measurement which involves the use of radioactive labeling of red cells. This is especially beneficial in cases when the hemoglobin level is between 16 and 20 g/dL.
Platelets and white blood cell count are also elevated. This is not very useful in the diagnosis of polycythemia itself but can be indicative of the risk of bleeding disorders.
Uric acid level is usually elevated due to the rapid turnover of cells, especially white blood cells. It is the product of cellular destruction and released in excess in cancers and other proliferative conditions since those cells tend to have a shortened lifespan. Uric acid crystals precipitate in the joints producing inflammatory pain and they are excreted by the kidney increasing the risk of urinary stones.
Reduced erythropoietin level: Erythropoietin is a hormone released by the kidney and functions to stimulate the bone marrow to produce more red cells. It is under the control of a feedback mechanism relating to the degree of blood oxygen concentration. Due to the increased red cell mass in polycythemia, the release of erythropoietin is suppressed. Renal functions should be assessed to make sure that this reduction is not due to a kidney problem.
Genetic testing: As mentioned before, the vast majority of polycythemia patients have JAK2 mutation. It is considered the backbone of polycythemia diagnosis.
Bone marrow biopsy: This isn’t a required test to diagnose polycythemia but can confirm the diagnosis and is considered a major criterion in the WHO diagnostic criteria of the disease. Findings will include a bone marrow with increased cellular component of the red cells, white cells and platelets.
To accurately diagnose polycythemia, doctors follow criteria established by the WHO in 2016 which are divided into major and minor ones.
- Major criteria include:
- Hemoglobin level of more than 16.5 g/dL in men and more than 16 g/dL in women, or a hematocrit level of more than 49% in men and more than 48% in women, or red cell mass > 25% above mean normal.
- Bone marrow biopsy showing hypercellularity for age with trilineage growth (panmyelosis) including prominent red cell, granulocytic white cell and platelet proliferation.
- Presence of JAK2V617F or JAK2 exon 12 mutation.
- While the minor criterion is:
- Serum erythropoietin level below the reference range for normal.
To diagnose polycythemia vera, all three major criteria must be fulfilled or the first 2 in addition to the minor criterion.