We were pleased to see so much attention given to air travel–related venous thrombo-embolism (VTE) in a recent issue of the ARCHIVES.1- 3 However, the accompanying editorial misquoted a misleading study.4 The editorial correctly notes that 2 randomized trials5,6 have demonstrated that compression stockings markedly reduce the incidence of deep vein thrombosis (DVT) during long-haul airplane flights. However, the editorial also cites the LONFLIT3 study,7 stating that these investigators randomized 200 high-risk passengers to low-molecular-weight heparin (LMWH) vs placebo and that the incidence of DVT was 4.8% in the control group vs 0% in the placebo group (P<.002). In fact, the LONFLIT3 study was underpowered and failed to demonstrate a statistically significant difference between the LMWH group and the placebo group in DVT incidence. The study enrolled 300 patients to 3 arms (100 patients each): an LMWH arm, a placebo arm, and a low-dose aspirin arm. A total of 249 subjects completed the study. Of the 82 evaluated patients assigned to placebo, 4 developed DVT compared with 0 of 82 patients receiving LMWH (P = .12 by Fisher exact test, 2-tailed). Three of the aspirin-treated patients developed DVT. After combining the aspirin and placebo groups, the authors still had statistically insignificant results (P = .10 compared with the LMWH group). Even after including superficial thrombophlebitis as thrombotic events, the results remained statistically insignificant (P = .07 for the LMWH group vs others). Finally, the authors used an inappropriate form of statistical analysis to double their sample size: they looked at each limb separately, although this maneuver violates necessary statistical assumptions of event independence. With 1 event in 164 LMWH-treated limbs and 14 events among 334 remaining limbs, the P value was.03 (not <.002, as stated in the abstract); this applies not to DVT specifically but to DVT plus superficial thrombophlebitis. The authors also claimed that there was a 25% risk reduction in DVT conferred by aspirin (3 DVTs in the aspirin group vs 4 in the placebo group) and that the P value for this comparison was <.05 (the correct P value is.72.).
Register and get free email Table of Contents alerts, saved searches, PowerPoint downloads, CME quizzes, and more
Subscribe for full-text access to content from 1998 forward and a host of useful features
Activate your current subscription (AMA members and current subscribers)
Purchase Online Access to this article for 24 hours
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Thank you for submitting a comment on this article. It will be reviewed by JAMA Internal Medicine editors. You will be notified when your comment has been published. Comments should not exceed 500 words of text and 10 references.
Do not submit personal medical questions or information that could identify a specific patient, questions about a particular case, or general inquiries to an author. Only content that has not been published, posted, or submitted elsewhere should be submitted. By submitting this Comment, you and any coauthors transfer copyright to the journal if your Comment is posted.
* = Required Field
Disclosure of Any Conflicts of Interest*
Indicate all relevant conflicts of interest of each author below, including all relevant financial interests, activities, and relationships within the past 3 years including, but not limited to, employment, affiliation, grants or funding, consultancies, honoraria or payment, speakers’ bureaus, stock ownership or options, expert testimony, royalties, donation of medical equipment, or patents planned, pending, or issued. If all authors have none, check "No potential conflicts or relevant financial interests" in the box below. Please also indicate any funding received in support of this work. The information will be posted with your response.
Some tools below are only available to our subscribers or users with an online account.
Download citation file:
Web of Science® Times Cited: 1
Customize your page view by dragging & repositioning the boxes below.
More Listings atJAMACareerCenter.com >
and access these and other features:
Enter your username and email address. We'll send you a link to reset your password.
Enter your username and email address. We'll send instructions on how to reset your password to the email address we have on record.
Athens and Shibboleth are access management services that provide single sign-on to protected resources. They replace the multiple user names and passwords necessary to access subscription-based content with a single user name and password that can be entered once per session. It operates independently of a user's location or IP address. If your institution uses Athens or Shibboleth authentication, please contact your site administrator to receive your user name and password.