Figure 11.5.a: Example of a ‘Summary of findings’ table

Summary of findings:

Compression stockings compared with no compression stockings for people taking long flights 

Patients or population: Anyone taking a long flight (lasting more than 6 hours)              

Settings: International air travel

Intervention: Compression stockings1

Comparison: Without stockings

Outcomes 

Illustrative comparative risks* (95% CI) 

Relative

effect

(95% CI) 

Number of
participants

(studies) 

Quality

of the

evidence

(GRADE) 

Comments 

Assumed risk

Corresponding risk

Without stockings 

With stockings 

Symptomatic
deep vein thrombosis
(DVT) 

See comment  

See comment  

Not estimable 

2821

(9 studies) 

See comment  

0 participants developed symptomatic DVT in these studies. 

Symptom-less

deep vein thrombosis

 

Low risk population 2 

RR 0.10

(0.04 to 0.26) 

2637

(9 studies) 

++++ 

High 

 

10 per 1000 

1 per 1000  

(0 to 3) 

High risk population 2 

30 per 1000 

3 per 1000  

(1 to 8) 

Superficial vein thrombosis 

13 per 1000

6 per 1000      

(2 to 15) 

RR 0.45

(0.18 to 1.13) 

1804

(8 studies) 

+++O

Moderate3 

 

Oedema

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

(95% CI –4.9 to –4.5). 

 

1246

(6 studies) 

++OO 

Low4 

 

Pulmonary embolus

See comment 

See comment 

Not estimable 

2821

(9 studies) 

See comment 

0 participants developed pulmonary embolus in these studies. 5

Death

See comment 

See comment 

Not estimable 

2821

(9 studies) 

See comment 

0 participants died in these studies.

Adverse effects 

See comment 

See comment 

Not estimable 

1182

(4 studies) 

See comment 

The tolerability of the stockings was described as very good with no complaints of side effects in 4 studies. 6 

 

 

 

 

 

 

 

*The basis for the assumed risk is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the intervention group and the relative effect of the intervention (and its 95% CI).

 CI:  Confidence interval;    RR:  Risk ratio     GRADE: GRADE Working Group grades of evidence (see explanations)   

1 1 All the stockings in the 9 trials included in this review were below-knee compression stockings. In four trials the compression strength was 20-30 mm Hg at the ankle. It was 10-20 mm Hg in the other four trials. Stockings come in different sizes. If a stocking is too tight around the knee it can prevent essential venous return causing the blood to pool around the knee. Compression stockings should be fitted properly. A stocking that is too tight could cut into the skin on a long flight and potentially cause ulceration and increased risk of DVT. Some stockings can be slightly thicker than normal leg covering and can be potentially restrictive with tight foot wear. It is a good idea to wear stockings around the house prior to travel to ensure a good, comfortable fitting. Stockings were put on 2 to 3 hours before the flight in most of the trials. The availability and cost of stockings can vary.

2 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 7 trials that excluded high risk participants was 1.45% and the incidence for the 2 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 1,000 respectively.

3 The confidence interval crosses no difference and does not rule out a small increase.

4 The measurement of oedema was not validated or blinded to the intervention. All of these studies were conducted by the same investigators.

5 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. 

6 None of the other 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 one trial.