IPSET-thrombosis score (essential thrombocythaemia)

What is measured: the risk of arterial or venous thrombosis, the main harm of essential thrombocythaemia. How: three items from the history and one blood test: age over 60, a previous thrombosis, cardiovascular risk factors (in the original score) and JAK2 V617F status by PCR. The revised IPSET-thrombosis (2015) defines very low risk (60 or under, no thrombosis, JAK2-negative), low (JAK2-positive only), intermediate (over 60 only) and high (any prior thrombosis, or over 60 with JAK2). The platelet count itself is not in the score, although counts above 1,000 to 1,500 x 10^9/L raise bleeding risk through acquired von Willebrand deficiency, and CALR-mutated patients clot less often. What a result changes: very low risk is observed, or given aspirin if cardiovascular risk factors are present; low risk gets low-dose aspirin; intermediate risk gets aspirin with cytoreduction considered; high risk gets cytoreduction (hydroxyurea first line, anagrelide, or interferon in younger patients and pregnancy) plus aspirin, and anticoagulation after a venous clot. Where it matters: essential thrombocythaemia.