This is an updated guideline on the diagnosis and management of polycythaemia vera (PV) from the British Society for Haematology. It was published in Nov 18. PV is the same as polycythaemia rubra vera and PCV.
Much of this is beyond what we need, but it outlines how we should be approaching a patient with raised haematocrit, which is useful.
If (like me) your understanding of PV is a bit sketchy, then patient.co.uk has a good reminder. In short, PV is a clonal haematological malignancy. It is caused by a mutation in a single haematopoietic stem cell. The JAK2 gene is mutated in nearly all PV.