Question

Which of the following is a major criterion for the diagnosis of polycythaemia vera?

• A. Presence of JAK-2 mutation
• B. Low erythropoietin levels
• C. High leucocyte alkaline phosphatase (increased LAP score)
• D. Thrombocytosis

Hint:

One driver mutation is a major WHO criterion, low EPO is only minor.

Answer 1

The Correct Option is A

Step 1: Recall the diagnostic framework for polycythaemia vera (PV). The WHO criteria are split into major and minor criteria. The major criteria are a raised haemoglobin or red cell mass, the presence of the JAK2 mutation, and characteristic bone marrow findings.
Step 2: Match the options. JAK2 V617F mutation is present in the great majority of PV patients and is listed as a MAJOR diagnostic criterion. So option A is a major criterion.
Step 3: Classify the others. A LOW serum erythropoietin level is a MINOR criterion, not a major one, although it is useful because it separates PV from secondary polycythaemia (where EPO is high).
Step 4: High leucocyte alkaline phosphatase (LAP) and thrombocytosis are supportive features often seen in PV, but they are not the formal major criteria asked for.
Step 5: Therefore the JAK2 mutation is the major criterion.
Answer: A. Presence of JAK-2 mutation.