Polycythemia

Polycythemia vera is a myeloproliferative disorder that need to be distinguished from other causes of increased haemoglobin level such as:

• Smoker's polycythemia
• Relative polycythemia - dehydration
• Secondary polycythemia - such as hypoxia, renal cell cancer which produces erythropoietin

In 2005, the JAK2-V617F mutation was described in the JAK2 gene. This mutation occurs in about 95% of patients with polycythemia vera. This mutation can also occurs in other myleproliferative disorders such as primary myelofibrosis or essential thrombocythemia, although they do not occur in the general population.

As a result, Current WHO diagnostic criteria was adjusted for the diagnosis of polycythemia vera as follows:

The presence of both major criteria and at least one minor criteria or the first major criteria and at least two minor criteria is required for a diagnosis of polycythemia vera.

The major criteria are:

1. Raised Haemoglobin lvel, haematocrit or red cell count
2. the presence of JAK2 gene

The minor criteria are:

• typical bone marrow histology
• low serum erythropoietin level
• formation of endogenous erythroid colonies on marrow culture

Diagnositic Algorithm:

If high haemoglobin level is found, repeat the haemoglobin test to determine if the raised level is borderline or transient.

If haemotocrit is less than or equal to 0.54 in men or 0.47 in women:
Consider causes other than polycythemia vera.

If haemotocrit is more than 0.54 in men or 0.47 in women:

• Firstly check oxygen satuation level, if less than 92% then it is likely due to secondary cause.
• If it is more than 92%, check for JAK2 gene mutation, erythropoietin level and/or bone marrow biopsy.