The “legacy” of the 125I-fibrinogen test and current management of isolated calf vein thrombosis

Prior to 1970 the true incidence of postoperative dep vein thrombosis (DVT) was unknown, although surgeons were aware that pulmonary embolism (PE) occurred in 1-4% of patients. The development of the 125I-Fibrinogen test in the 1970s provided a means of screening surgical patients and demonstrated that the incidence of silent DVT varied from 17-47% depending on age, type and duration of operation. Only 4-6% of the patients with DVT developed symptoms. It has now been realised that although symptomatic isolated calf DVT is rarely associated with fatal PE, it produces local damage to venous valves with the development of reflux and post-thrombotic syndrome in 10-23% of patients and has a recurrence rate of 14%. In recent systematic reviews and meta-analyses of patients with symptomatic isolated calf DVT anticoagulation therapy up to 3 months reduces the incidence of recurrent DVT from 7.9% to 1.65% (RR 0.25; 95% CI 0.10-0.67). When anticoagulation period of 3 months was compared with 6 weeks it reduced the incidence of DVT from 14.4% to 4.8% (RR 0.32; 95% CI 0.16-0.64) Current guidelines of European Society of Vascular Surgery are as follows: “For patients with symptomatic calf DVT 3 months therapy is recommended over shorter durations (Class 1, Level A).