Analysis of risk factors predicting thrombotic and/or haemorrhagic complications in 306 patients with essential thrombocythemia.

Thrombotic and haemorrhagic complications are the main causes of morbidity in Essential Thrombocythemia (ET). We investigated the clinical and laboratory characteristics associated with the occurrence of these events with the aim of identifying subgroups of patients who might benefit from anti-aggregant and/or cytoreductive therapy. The study involved 306 consecutive ET patients (median age 58 years and median follow-up 96 months); the investigated variables were age, gender, platelet count, previous history of thrombotic or haemorrhagic events, disease duration and cardiovascular risk factors. Forty-six patients (15%) experienced thrombotic complications during the follow-up: 26/64 patients with a previous history of thrombosis (40.6%) and 20/242 patients without (8.3%; p < 0.0001). Thirty-one patients (10%) experienced major haemorrhagic complications, mainly gastrointestinal tract bleeding: 3 with and 28 without a history of haemorrhagic events (p = 0.052). When the patients with a negative history of thrombosis were stratified on the basis of the number of cardiovascular risk factors (none vs. one vs. more than one), there was a significant correlation with the occurrence of thrombotic events (p < 0.05). ET patients with a positive history of thrombosis are at high risk of thrombotic complications, and should receive cytoreductive and anti-aggregant treatment. Asymptomatic patients with a negative thrombotic history and no cardiovascular risk factors are at low risk, and should not be treated. Patients with a negative thrombotic history and one or more cardiovascular risk factors are at intermediate risk, and should be treated with anti-aggregant and/or cytoreductive therapy. The need for treatment should be periodically re-evaluated. Age and platelet count, generally accepted as very important risk factors for thrombosis, did not seem in our series associated with an increased risk for thrombosis.