Question:medium
Which of the following is a major criterion for the diagnosis of polycythaemia vera?
Which of the following is a major criterion for the diagnosis of polycythaemia vera?
Show Hint
One driver mutation is a major WHO criterion, low EPO is only minor.
Updated On: Jun 24, 2026
- Presence of JAK-2 mutation
- Low erythropoietin levels
- High leucocyte alkaline phosphatase (increased LAP score)
- Thrombocytosis
Show Solution
The Correct Option is A
Solution and Explanation
Polycythaemia vera is diagnosed by the WHO checklist, which groups findings into major and minor. The question simply asks which listed feature falls in the major group.
The major criteria centre on three things: an increased red cell mass or haemoglobin, the presence of the JAK2 mutation, and a typical hypercellular trilineage marrow. Of the four options, the JAK2 mutation is the one that sits squarely in this major group, since it is found in nearly all PV patients and drives the disease.
The rest are weaker pieces of evidence. A low erythropoietin level is only a minor criterion, useful mainly to rule out secondary causes where EPO would instead be high. A raised LAP score and a high platelet count are commonly seen but are supportive clues rather than formal major criteria. So the JAK2 mutation is the correct major criterion.
\[\boxed{\text{A. Presence of JAK-2 mutation}}\]
The major criteria centre on three things: an increased red cell mass or haemoglobin, the presence of the JAK2 mutation, and a typical hypercellular trilineage marrow. Of the four options, the JAK2 mutation is the one that sits squarely in this major group, since it is found in nearly all PV patients and drives the disease.
The rest are weaker pieces of evidence. A low erythropoietin level is only a minor criterion, useful mainly to rule out secondary causes where EPO would instead be high. A raised LAP score and a high platelet count are commonly seen but are supportive clues rather than formal major criteria. So the JAK2 mutation is the correct major criterion.
\[\boxed{\text{A. Presence of JAK-2 mutation}}\]
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