"What is already known on this topic" is incorrectly stated
In their interesting paper, Kelman et al (1) stated that: "Venous
thromboembolism has been suggested to be up to four times more likely to
develop within two to four weeks of a flight". This statement is not
supported by any evidence and is in fact misleading.
The only reference in the literature to quote the risk as high as
four was of Ferrari et al (2) and this reference of high risk of DVT in
air travel was quoted by Kelman et al(1)in their introduction section.
Ferrari et al (2) stated the odds ratio of 3.98, 95% CI (1.9-8.4) for
the increased risk of DVT in relation to ANY TRAVEL in their case control
study. There were 39/160 of DVT in relation to any travel and 12/160 in
the control group. All journeys undertaken during the preceding 4 weeks
and lasting > 4 hours by whatever means of transport were considered
and not two to four weeks of a history of flight as it was stated by
Kelman et al (1). In fact out of the 39 cases of DVT in relation to
travel, there were 2 cases in which the travel was by train, 9 by airplane
29 in cars.
Furthermore, Ferrari et al (2) study used a control group of patients
who were admitted to a cardiology department, and therefore the control
individuals might be too ill in the last four weeks to have travelled and
this was the reason that could explain the high odds ratio they reported
in relation to travel.
1. Kelman CW, Kortt MA, Becker NG, Li Z, Mathews JD, Guest CS, Holman
CD. Deep vein thrombosis and air travel: record linkage study. BMJ
2003;327:1072-1075.
2. Ferrari E, Chevallier T, Chapelier A, Baudouy M. Travel as a risk
factor for venous thromboembolic disease: a case-control study. Chest
1999;115:440-4.
Competing interests:
None declared
Competing interests:
No competing interests
01 December 2003
Dr Y Adi
Systematic Reviewer
Department of Public Health & Epidemiology, University of Birmingham, B15 2TT
Rapid Response:
"What is already known on this topic" is incorrectly stated
In their interesting paper, Kelman et al (1) stated that: "Venous
thromboembolism has been suggested to be up to four times more likely to
develop within two to four weeks of a flight". This statement is not
supported by any evidence and is in fact misleading.
The only reference in the literature to quote the risk as high as
four was of Ferrari et al (2) and this reference of high risk of DVT in
air travel was quoted by Kelman et al(1)in their introduction section.
Ferrari et al (2) stated the odds ratio of 3.98, 95% CI (1.9-8.4) for
the increased risk of DVT in relation to ANY TRAVEL in their case control
study. There were 39/160 of DVT in relation to any travel and 12/160 in
the control group. All journeys undertaken during the preceding 4 weeks
and lasting > 4 hours by whatever means of transport were considered
and not two to four weeks of a history of flight as it was stated by
Kelman et al (1). In fact out of the 39 cases of DVT in relation to
travel, there were 2 cases in which the travel was by train, 9 by airplane
29 in cars.
Furthermore, Ferrari et al (2) study used a control group of patients
who were admitted to a cardiology department, and therefore the control
individuals might be too ill in the last four weeks to have travelled and
this was the reason that could explain the high odds ratio they reported
in relation to travel.
1. Kelman CW, Kortt MA, Becker NG, Li Z, Mathews JD, Guest CS, Holman
CD. Deep vein thrombosis and air travel: record linkage study. BMJ
2003;327:1072-1075.
2. Ferrari E, Chevallier T, Chapelier A, Baudouy M. Travel as a risk
factor for venous thromboembolic disease: a case-control study. Chest
1999;115:440-4.
Competing interests:
None declared
Competing interests: No competing interests