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Evidence-based Care: Importance of Monitoring Counts and Tracking Trends in Advanced Polycythemia Vera (PV)

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PV is a hematologic cancer that may be associated with elevated blood counts including hematocrit and white blood cell (WBC) count. Previous studies of patients with PV have suggested that hematocrit >45% and WBC count >11 x 109 may be associated with increased risk of thrombosis. It is important to monitor hematocrit and WBC count and also to watch for trends in these counts as part of assessing the effectiveness of therapy in patients with PV.

When I'm reviewing a CBC, first of all, I am looking at the hematocrit because I do know that strict control of hematocrit less than 45% is key for reducing thromboembolic events and cardiovascular events. This is based on the CYTO-PV study.

The next thing I look at is white blood cell count. So there was a multivariate analysis within the same study that showed that white blood cells greater than 11,000 was also associated with increased risk of thrombotic events.

My goals for patients with advanced polycythemia vera are to manage their counts, to reduce risk of thromboembolic events, ensuring that their hematocrit stays less than 45% and their white blood cells stay less than 11,000.

So I have to look at what treatment strategy we're using and then, monitoring the trends is really the most important thing. And so, if I have a patient that I'm seeing weekly, for example, and their hematocrit is going up and up and up, then maybe in a month I'm saying, "Okay, we need to maybe implement some new strategies here." Also, in patients perhaps who have been very stable for a while, you know, maybe 3 months of increasing hematocrit levels to the point of needing phlebotomy or perhaps increasing white blood cells, that would really indicate to me that there needed to be perhaps a change.

When I am looking at a patient over time, it actually varies per patient. So I have to look at what treatment strategy we're using and then, monitoring the trends is really the most important thing.

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Lindsey Lyle, MS, PA-C Physician Assistant and Senior Instructor University of Colorado Cancer Center | Aurora, CO
Ms Lyle's clinical focus includes benign hematologic disorders and hematologic malignancies, with a special interest in myeloproliferative neoplasms (MPNs). Her clinical philosophy focuses on treating the person as a whole, taking every aspect of a patient’s physical and mental health into consideration during diagnosis and treatment. A national and regional speaker on hematologic malignancies, she is also involved in rural health outreach and improving health literacy among young people.