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I saw Mr. Smith almost two years ago. He was admitted at Citrus Memorial hospital for a clot in his leg. He was 63 years old and fairly healthy at that time.
I was consulted to do further workup. When he came for follow-up in my office, his RBC (red blood cell) count as measured in CBC by hemoglobin and hematocrit were mildly elevated.
I ordered a blood test called the JAK-2 gene test. It was positive. He also had low erythropoietin level.
This is diagnostic of a bone marrow problem called polycythemia rubra vera.
It is a disorder of the bone marrow. It mainly causes too much production of red blood cells, although the numbers of white blood cells and platelets are also increased. It is a rare disease that occurs more often in men than women, and is rare in patients younger than 40.
In polycythemia vera, patients produce an excessive number of otherwise normal red blood cells, raising blood volume and viscosity which, in turn, creates a range of clinical problems.
These include increased rates of major thrombotic events, such as a clot in the leg or DVT, as happened in my patient. It also increases the risk of stroke. The condition can also progress to leukemia or myelofibrosis (scar in bone marrow).
The treatment includes periodic phlebotomy to bring down the hematocrit to less than 45. Some patients also need a medication called Hydroxyurea.
An interesting research was reported at the American Society of Hematology’s annual meeting. The findings were published simultaneously online in the New England Journal of Medicine.
The study consists of 365 patients who were prospectively randomized to keep either hematocrit less than 45 in one group or between 45 and 50 in another group. At study entry, phlebotomy was employed in about two-thirds of patients in both treatment arms, and about half received hydroxyurea, also with no difference between groups.
With median follow-up of 31 months, five patients in the low-hematocrit group and 18 in the high-hematocrit arm had death or major thrombotic (clotting) event. Researchers calculated incidence rates for the major clotting outcome of 1.1 per 100 patient-years for the low-hematocrit group versus 4.4 per 100 patient-years with the higher target.
In other words, if we keep hematocrit below 45, it cuts down major clotting events by one fourth.
Dr. Spivak, however, wished for more detailed analyses of possible gender differences. “Women normally have a lower red-cell mass and hematocrit than men, and women with polycythemia vera are at risk for intra-abdominal venous thrombosis (clot in major vein in the abdomen) with an apparently normal hematocrit,” he wrote in the editorial.
“Therefore, the hematocrit target described by Marchioli et al. is adequate for men but inadequate for women, who on the basis of other studies should have a target hematocrit of less than 42%.”
My patient is on periodic phlebotomy and is doing well.
Dr. Sunil Gandhi is a hematologist and oncologist. He is volunteer medical adviser of the Citrus Unit of American Cancer Society. Write to 521 N. Lecanto Highway, Lecanto, FL 34461, email email@example.com or call 352-746-0707.