New diagnostic criteria -PV
Subject: PV criteria
Helen and all,
I hope I wasn't too confusing - anyway I thought perhaps some
clarification might help (for example, Helen, in the 3 PVSG criteria it
would be high hematocrit due to increased RCM). So please find below some
new criteria for diagnosing polcythemia vera taken from LEUKEMIA AND
LYMPHOMA, 1996 by Pearson and Messinezy. They mention that the original
PVSG criteria is 20 years old and needs to be updated (which they then do).
I have included the old PVSG criteria in parentheses as applicable and
added some notes at the bottom.
Major criteria:
1. Increased red cell mass greater than 25% above the patient's mean
normal predicted value based on surface area. (The old PVSG used an older
method of detecting RCM and said equal or above 36 mL/kg for males; 32
ml/kg for females.)
2. Absence of a cause of secondary polycythemia (The old PVSG used
arterial oxygen saturation of above 92% here.)
The above two criteria are considered essential - in addition, a third
major criteria being;
3. Palpable splenomegaly OR a marker of clonal hematopoiesis (chromosome
abnormality). (The old PVSG just used splenomegaly here.)
The diagnosis of PV is considered supported with all of the above three
criteria (the first two, and one of the third). HOWEVER, if only the first
2 major criteria exist, then two minor criteria (below) should be present
to secure diagnosis.
Minor criteria:
1. Platelet count above 400,000
2. Neutrophil count above 10 (The PVSG had leukocytosis above 12 with no
fever or infection.)
3. Splenomegaly confirmed by a scanning technique
4. BFU-E growth (BFU-E is burst-forming unit- erythroid; this goes along
the line of the endogenous erythroid colony (EEC) test.)
5. Reduced serum erythropoietin level
The old PVSG minor criteria were the first two as noted above and then
dealt with elevated LAP or vitamin B12 levels for the other minor criteria.
So, to repeat, Pearson & Messinezy are suggesting that either all of the
three major criteria should be present OR the first two major criteria with
two minor criteria for a diagnosis of polycythemia vera.
NOTES: None of the criteria listed require a biopsy. However, if red cell
mass is not performed before phlebotomy, then it is not valid. (According
to sources - biopsy IS valuable, if necessary, to determine P.vera
diagnosis as opposed to other types of polycythemia. However, it may not be
that valuable in determining between P. vera and essential thrombocythemia.
References available.)
The newer red cell mass/plasma volume tests (preferred by
Pearson/Messinezy & also mentioned in other articles) take into account
body height & obesity (I don't understand it all); it is also mentioned in
articles that seasonal variations, exercise, time of day, obesity, smoking,
etc., can affect these measurements.
Also note that where the older PVSG major criteria number two was just to
confirm the oxygen level - the new criteria listed by P & M says that
secondary causes should be ruled out (an oxygen saturation test does not by
itself rule out all known causes of secondary polycythemia).
And, under the new minor criteria # 4, though the BFU-E (or EEC) listed
would fit in as being tested from the peripheral blood (just from blood
drawn); if used from marrow blood (collected from aspiration - as with a
biopsy) - some sources have said it would then be a positive indicator of
polycythemia vera (references available).
A normal or elevated erythropoietin level would be more indicative of a
secondary polycythemia (with a reduced level indicating P. Vera). It's
just a minor criteria, though, since overlap can occur.