Anemone study: prevalence of risk factors for superficial vein thrombosis in a large Italian population of blood donors.

Knowledge of the distribution of risk factors for superficial thrombosis (SVT) in low-risk population is fundamental to improve the prevention of the disease in each individual and high-risk settings of patients. Exact frequency data for the low-risk population are scarce, but could be useful for optimal use of prophylactic strategies against venous thrombosis. Blood donors represent a low-risk population, because are healthier than the general population. The objective of this study was to assess the prevalence of vein thrombosis, particularly SVT, and associated risk factors in a low-risk population such as blood donors. In this multicentre cross-sectional study, donors from six Italian blood banks responded to a self-administered questionnaire. The enrolment lasted from 1st June 2017 to 30th July 2018. History of vein thrombosis was referred by 89 (0.76%) individuals, (49 men) with an age-dependent effect. The prevalence reached 2.9% in women and 0.8% in men aged ≥ 49 years, with a significant difference only for women. After controlling for potential confounders, a significant and independent association was found between a history of vein thrombosis and age (OR: 1.03, 95%CI 1.01-1.05), varicose veins (OR: 15.8, 95%CI 7.7-32.6), plaster cast/bed rest (OR: 2.3, 95% CI 1.0-5.3) and transfusion (OR: 5.1, 95% CI 1.3-19.5). This study shows that low-risk individuals share the same risk factors for SVT as patients in secondary care. It also suggests that transfusion confers an increased risk of SVT in healthy population.