Harry P. Erba, MD, PhD: Jamile, we have identified a specific hematocrit hemoglobin level above which we do not want to see our patients. Can you review for us the data that support that? How often do you have to check if the patient is above that level, and when do you intervene?

Jamile M. Shammo, MD, FASCP, FACP: There are data to suggest that optimization of the hematopoietic parameters in patients who have PV [polycythemia vera] are extremely important. In fact, let me start with the hematocrit, for example. There are data that came from the CYTO-PV study that suggests that maintaining a hematocrit level below 45% is associated with a 4-fold decrease in mortality from cardiac event and major thrombotic events, and that’s something we can easily do as practitioners, as hematologists: maintain the hematocrit below 45%.

How often should you look for that? It depends on the stage of the disease. If you’re starting a new patient on phlebotomy, for example, you might do it twice a week and have someone checking those numbers twice a week. As the disease goes on or as you’re getting closer to optimization, the frequency of checking the hematocrit becomes less and less. We have to try as much as possible to keep this below 45%. I don’t want to put my patients at risk by that parameter.

The other thing is the platelet count. Practitioners have to realize that, as you phlebotomize patients, the platelet count is likely to go up; we’re inducing a state of iron deficiency by doing phlebotomy. People get nervous, and then they start to think, “Now the platelet count is rising.” The only issue there is perhaps the platelet count interfering with the administration of antiplatelet therapy.

It’s OK to have a mildly elevated platelet count, and it’s OK to give aspirin. But if you’re concerned, you could check for acquired Von Willebrand factor deficiency. I always worry that perhaps trying to chase the platelet count in the setting of phlebotomy may be misleading to some in terms of initiation of other treatments, or even suggesting that maybe this isn’t a disease that’s responding.

Finally, leukocytosis is something we need to pay attention to, because it is an indicator of myeloproliferation. For some people, there’s a lot of debate about whether they may be associated with increasing thrombotic events, mostly with data pointing to retrospective analysis of the association between leukocytosis and thrombotic events.

We [at Rush University Medical Center] did 520 patients who had PV, and we looked at the risk and didn’t find it in this retrospective analysis. These were private institutions that submitted data to evaluate that piece, but what it was associated with is disease progression. It’s something we need to pay attention to. Perhaps if you have ongoing leukocytosis, maybe this would be the time to evaluate the patient fully and see exactly if there is progression. Are they compliant with their medication? We don’t even talk about that. We then move forward. The most important piece when it comes to blood counts is that.

Any time you talk about MPNs [myeloproliferative neoplasms], there’s also this piece about splenomegaly and a piece about constitutional symptoms. Every time you see patients in the clinic, those would be things that we need to pay attention to, to assess how is disease doing and what we need to pay attention to in terms of disease control.

Transcript Edited for Clarity