Studies that reported short-term (immediate periprocedure period) or long-term venous thromboembolism outcomes following IVC filter replacement (with and without concomitant anticoagulation therapy) were eligible for inclusion. Studies were included regardless of whether there were sufficient data to calculate the rate of venous thromboembolism. Randomised controlled trials (RCTs), prospective cohort studies, retrospective cohort studies and case-control studies were eligible.
The included studies used Gunther, Greenfield, Vena Tech-LGM, Simon nitinol or Bird's Nest filters. Mean follow-up ranged from 12 days to nine years (where reported). In most studies, whether or not patients received anticoagulation therapy appeared to be based on physician judgement. Methods used to assess presence of venous thromboembolism varied within and between studies. More than half of the studies used at least one of routine abdominal radiograph, duplex ultrasound, contrast venography and ventilation-perfusion scan. Some studies performed imaging only on clinical suspicion, clinical follow-up only or the method of outcome assessment was not reported; there was some form of radiologic follow-up of 33% of patients, clinical follow-up only of 42% and unspecified method of follow-up for 25%.
Study selection appeared to be undertaken independently by two reviewers.