Summary of findings for the main comparison.
Compression stockings compared with no compression stockings for people taking long haul flights
| Does wearing compression stockings prevent deep vein thrombosis in people taking long haul flights? | ||||||
| Patient or population: passengers on a long haul flight (more than 4 hours) Setting: long haul flights Intervention: wearing compression stockings1 Comparison: not wearing stockings | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | Number of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Risk with not wearing compression stockings | Risk with wearing compression stockings | |||||
| Symptomatic deep vein thrombosis (DVT) Follow‐up period immediately post flight to 48 hours |
0 participants developed symptomatic DVT in these studies | Not estimable | 2821 (9 studies) |
Not estimable² | ||
| Symptomless DVT Follow‐up period immediately post flight to 48 hours |
Low‐risk population3 | OR 0.10 (0.04 to 0.25) | 2637 (9 RCTs) | ⊕⊕⊕⊕ HIGH | ||
| 10 per 1000 | 1 per 1000 (0 to 3) | |||||
| High‐risk population2 | ||||||
| 30 per 1000 | 3 per 1000 (1 to 8) | |||||
| Pulmonary embolism (PE) Follow‐up period immediately post flight to 48 hours |
0 participants developed symptomatic PE in these studies | Not estimable | 2821 (9 studies) |
Not estimable2 | ||
| Death Follow‐up period immediately post flight to 48 hours |
0 participants died in these studies | Not estimable | 2821 (9 studies) |
Not estimable2 | ||
| Superficial vein thrombosis Follow‐up period immediately post flight to 48 hours |
Study population | OR 0.45 (0.18 to 1.13) | 1804 (8 RCTs) | ⊕⊕⊕⊝ MODERATE4 | ||
| 13 per 1000 | 6 per 1000 (2 to 15) | |||||
| Oedema Follow‐up period immediately post flight Post flight values measured on a scale from 0 (no oedema) to 10 (maximum oedema) |
The mean oedema score ranged across control groups from 6 to 9 |
The mean oedema score in the intervention groups was on average 4.7 lower (4.9 lower to 4.5 lower) | ‐ | 1246 (6 RCTs) | ⊕⊕⊝⊝ LOW5 | It was not possible to pool data from an additional 2 studies (Hagan 2008; Loew 1998). These both reported reduced oedema post flight in the stocking group6 |
| Adverse effects arising from the use of compression stockings Follow‐up period immediately post flight |
The tolerability of the stockings was described as very good with no complaints of side effects in 4 studies | Not estimable | 1182 (4 studies) |
Not estimable | None of the trials reported adverse effects, apart from 4 cases of superficial vein thrombosis in varicose veins in the knee region that were compressed by the upper edge of the stocking in 1 trial. However, the meta‐analysis of the data on this outcome from this trial and 7 others found a non‐statistically significant difference (see above) | |
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; DVT: deep vein thrombosis; PE: pulmonary embolism; OR: Odds ratio | ||||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect | ||||||
1 Stockings in the nine trials included in the meta‐analysis were below‐knee compression stockings. In four trials the compression strength was 20 to 30 mmHg at the ankle. It was 10 to 20 mmHg in the other four trials. One trial not included in the meta‐analysis used graduated compression tights. See Characteristics of included studies for details.
2 If there are very few or no events and the number of participants is large, judgement about the quality of evidence (particularly judgements about precision) may be based on the absolute effect. Here the quality rating may be considered 'high' if the outcome was appropriately assessed and the event, in fact, did not occur in 2821 studied participants.
3 Two trials recruited high‐risk participants defined as those with previous episodes of DVT, coagulation disorders, severe obesity, limited mobility due to bone or joint problems, neoplastic disease within the previous two years, large varicose veins or, in one of the studies, participants taller than 190 cm and heavier than 90 kg. The incidence for seven trials that excluded high‐risk participants was 1.45% and the incidence for the two trials that recruited high‐risk participants (with at least one risk factor) was 2.43%. We have rounded these off to 10 and 30 per 1000 respectively.
4 Downgraded by one level ‐ the confidence interval crosses no difference and does not rule out a small increase.
5 Downgraded by two levels ‐ the measurement of oedema was not validated or blinded to the intervention. All of these studies included in the meta‐analysis were conducted by the same investigators.
6 In Hagan 2008, oedema was measured by calculating the change in ankle circumference before and after landing; stockings versus no stockings. Loew 1998 used a clinical scale and between‐individual comparison as the passengers wore a stocking on one leg only.