ABO BLOOD-GROUPS AS RISK-FACTORS FOR THROMBOSIS

To evaluate the relationship between ABO blood group and thrombosis, w e studied 127 patients taking oral anti-vitamin K drugs for thromboemb olism prophylaxis and compared them with 700 voluntary blood donors. T here were 68 patients with venous thrombosis (VT)-68 with deep vein th rombosis and 8 with pulmonary embolism-and 51 patients with arterial e mbolism (AE). There were 61 men and 66 women. Mean age at diagnosis wa s lower for all women, regardless of if they had VT or AE (43 years) t han for men (55 years; Kruskal-Wallis test, p < 0.01). There was an im balance between blood group A and O frequencies in patients with VT ve rsus blood donors, with a higher frequency of blood group A or a lower frequency of blood group O, represented by a high A/O ratio. A/O rati o for blood donors was 0.63; it was 1.50 for men (Fisher test, p = 0.0 28) and 1.44 for women (Fisher test, p = 0.010). Patients with AE show ed the same discrepancy, but it was significant for women (A/O = 2.25; Fisher test, p = 0.026) and not for men (A/O = 0.86; Fisher test, p = 0.836), suggesting that men with AE might have other risk factors for thrombosis. These data are not conclusive about the causes of the ass ociation between ABO blood groups and thrombosis, and prospective stud ies are needed to verify whether blood typing could have a predictive value for prophylatic measures in clinical and surgical patients.