A Cochrane review included 2 studies with a total of 529 subjects. One open quasi-randomised trial of 129 participants with traumatic hip fractures showed a reduction in pulmonary embolism (PE) (RR 0.3, 95% CI 0.11 to 0.82), but not mortality (RR 0.41, 95% CI 0.15 to 1.16) over a 34 day period in the filter group. The another trial was an open RCT of 400 participants with documented proximal deep vein thrombosis (DVT) or PE who received concurrent anticoagulation. Permanent caval filters prevented PE at eight years (HR 0.37, 95% CI 0.17 to 0.79). No reduction in mortality was seen, but this reflected an older study population (mean age 73 years); the majority of deaths were due to cancer or cardiovascular causes. There was an increased incidence of DVT in the filter group (HR 1.52, 95% CI 1.02 to 2.27). Adverse events were not reported.
Comment: The quality of evidence is downgraded by imprecise results (few patients and wide confidence intervals; few outcome events) and by indirectness (indications for filter insertion and filter types differ from the current clinical practice; today retrievable filters are increasingly used).