LONFLIT 5.

Study characteristics
Methods	Trial design: randomised controlled trial (parallel). Country principal investigators: Italy, UK, Australia. Where trial conducted: UK. Date of trial: October 2002 to January 2003. Multi‐centre: yes. Blinding: outcome assessor not blinded. Lost to follow‐up: 13/191 (stocking), 17/197 (control); dropouts due to low compliance or flight connection problems.
Participants	Inclusion criteria: 446 high‐risk participants were contacted. High risk included previous episodes of DVT or superficial vein thrombosis, coagulation disorders, severe obesity or limited mobility due to bone or joint problems, neoplastic disease within the previous 2 years, clinical cardiovascular disease and large varicose veins. Participants were recruited through flight shops. Exclusion criteria: participants taller than 190 cm, weighing more than 90 kg, recent or presence of thrombosis, severe bone, joint, or mobility problems, severe hypertension, or clinical disease requiring treatment. No. randomised: 388. No. analysed: 358. Age (years): mean 45, SD 12 (stocking); mean 45, SD 11(control). Sex: 55% M (stocking), 66% M (control) ‐ based on number analysed.
Interventions	Stocking Group Type of stocking: below‐knee Scholl flight socks UK with 14 to 17 mmHg of pressure at the ankle. Stockings were put on 3 to 4 hours before the flight. No. randomised: 191. No. analysed: 178. Length of flight: 11 to 13 hours. Type of seat: Economy, seat pitch 31 inches. Route and time of flight: London to Narita (Japan). Additional interventions: suggestions were given to participants. An exercise plan and educational video were given to all participants which included advice on mild exercise, drinking regularly and avoiding placing baggage under seats. Control Group Type of control: no intervention. No. randomised: 197. No. analysed: 180. Length of flight: 11 to 13 hours. Type of seat: Economy, seat pitch 31 inches. Route and time of flight: London to Narita (Japan). Additional interventions: the same advice as the stocking group was given.
Outcomes	Outcomes assessed: incidence of DVT and SVT DVT diagnosed by: D‐dimer and fibrinogen tests which were performed before (within 12 hours) and after the flight (within 4 hours) (Dade Dimmertest, Latex Test, Behring, Germany). This was done by compressing the major veins (femoral, popliteal and tibial). Site of DVT: Stockings group: distal, below knee vein (2); Control group: location not reported for 7 in most recent report but the locations for the 6 reported in the first article were distal superficial femoral (3), popliteal (2), soleal (1). All DVTs were asymptomatic. Site of SVT: site not reported for the 5 (control). Other investigations performed: none reported. Additional complications reported: none.
Funding	Not reported.
Declarations of interest	Not reported.
Notes	See Feedback.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	States randomised but no further details
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not possible
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	All accounted for
Selective reporting (reporting bias)	Low risk	All expected outcomes reported
Other bias	Low risk	No evidence of other bias