The first factor is the number of blasts you have in your bone marrow. If you have less than 5 percent blasts, then your IPSS blast score is 0. If you have 5 to 10 percent, then your IPSS blast score is 0.5. If you have 11 to 20 percent, then your IPSS blast score is 1.5. If you have 21 to 30 percent, then your IPSS blast score is 2.0.