My appointment for the red cell mass test is confirmed for the following week. Dr. Silver stressed that it is important I do not cancel once the materials are ordered. This is a very old nuclear medicine test that uses radioactive iodine and radioactive chromium. Very few hospitals have the ability to conduct the test because of the very technical nature.
Albert was the phlebotomist assigned to me. He explained he would draw some blood which would be sent to the lab. The lab would attach the iodine to select red cells and the chromium to plasma cells. This would take about an hour. My radioactive blood would be injected into my body and at specific intervals of about 15 minutes each the blood drawn again about 4 times. The test takes about 2 hours to conduct. The test will measure the plasma and red cells that have been tagged with isotopes. Using sophisticated math and my precise body weight and body mass index, the test will determine my true hematocrit, not just the peripheral htc measured in a usual CBC test. If my red cell mass is greater than 125 percent of the predicted value for someone of my size and my erythropoietin level is below normal the dx will be PV. If not it must be ET.
The correct diagnosis is critical. Treatment protocols while very similar are different for PV and ET.
Both diseases can be treated with hydroxy urea, Pegasus, and anegrelide, however only PV uses phlebotomies to reduce red cell lines. Phlebs will cause an elevation in platelets and for this reason are not appropriate for ET patients.
The day arrived to meet Dr. Silver again and review the results. Waiting in the exam room Dr. Silver poked his head in and simply said, it's good news! My erythropoietin level was low, a 3, indicating the jak2 mutation was causing the proliferation of red cells, suggesting a PV diagnosis. However the real key was the red cell mass. Mine is 106 percent. Clearly not high enough for a PV dx. Therefore the winner is ET!!!
My dx had been confirmed. Dr. Silver cautioned that I may transform into PV at some time in the future because of the low epo but for now it's ET. The treatment plan is careful monitoring every three months and a daily baby aspirin.