March 18th, 2013

Vena Cava Filters: Little Evidence and Wide Variation in Use

Despite the absence of any evidence demonstrating benefit or showing how best to use them, vena cava filters (VCF) are used in most hospitals. Now a new study published in JAMA Internal Medicine suggests that this same lack of evidence results in an extremely broad rate of use in different hospitals. An accompanying viewpoint raises the question: “How could a medical device be so well accepted without any evidence of efficacy?”

Researchers conducted a retrospective observational study that compared the frequency of VCF use in 236 California hospitals by analyzing data from 130,643 acute VTE hospitalizations over four years. Overall, the rate of VCF placement was 14.95%, but there was a very broad variation in the percentage of acute VTE cases in which a VCF was placed, from 0% to 38.96%. The authors said that this finding places VCF “among surgical procedures with the greatest variation in geographic studies in the United States.” Even after adjusting for differences in patient populations between hospitals, the variation between hospitals remained significant.

Overall, VCF was more likely to be used in people who had acute bleeding at admission, who required a major operation after admission for VTE, who had metastatic cancer, and who had extreme severity of illness. Smaller hospitals, rural hospitals, and private hospitals not in the Kaiser system were more likely to use VCFs.

There was no significant difference in VCF use between for-profit and not-for-profit hospitals, “suggesting that the wide variation in VCF use is not likely explained by exploitation of the fiscal benefits of VCF placement by for-profit private hospitals.” Further, both socioeconomic factors and geographic location did not appear to influence the likelihood that a hospital would use VCFs. The authors wrote that “these findings suggest that an important factor affecting the use of VCFs is the local culture and practice pattern within each hospital. Although we could not gather reliable data regarding the number of interventional radiologists or vascular surgeons who work at each hospital, one possible explanation for the higher frequency of VCF use in larger private hospitals is the availability of specialists who are skilled in inserting these devices.”

In a second study, Shayna Sarosiek  and colleagues performed a retrospective review of 952 patients who received a retrievable VCF at Boston Medical Center. Despite VCF placement, 7.8% of the patients had a venous thrombotic event. Although many of the devices were placed “because of a perceived contraindication to anticoagulants,” fully a quarter of the patients were receiving anticoagulant therapy at the time of discharge. Only a small percentage (8.5%) with retrievable VCFs had their filter removed successfully.

In their editorial, Vinay Prasad, Jason Rho, and Adam Cifu observe that despite  their “poor evidence base” VCF filters have never been rigorously reviewed by the FDA, because the first devices were developed prior to the premarket approval process and all subsequent devices have  gained approval based on the far less burdensome 510(k) process. Despite the need for randomized controlled trials of VCFs, “there is little incentive for manufacturers of filters to embark on trials that can only eliminate their products’ market share. Therefore, we need either the FDA to require current filter manufacturers to perform efficacy studies of their devices as a condition for remaining on the market or a large federally funded study to determine if this expensive device leads to greater benefit than harm. Until then, clinicians and patients face difficult choices. Follow current standard of care and place filters where guidelines advise, or do not place filters, after informed consent informs patients that there is evidence of harm without evidence of benefit.”

One Response to “Vena Cava Filters: Little Evidence and Wide Variation in Use”

  1. Thomas Kline, Md phd says:

    It is amazing how comfortable people get with therapies and approaches
    that have no scientific basis. This is guild behavior not professional
    behavior. We used to bleed people, stick leeches on them – all to
    “do something” for our own comfort zones. The biggest failing
    of medicine as a trade and not as a profession is refusing to believe
    that a disruption in our “ways of doing things” is actually good for
    our patients. Studies upon studies have shown unprofessional resistance
    to the facts.

    There needs to be a course in our trade schoolsm that is our medical schools,on the difference between professionals and tradesman.