Ginsberg 2001.

Methods	Study design: randomised double‐blind clinical trial Method of randomisation: prerandomisation stratification applied, randomisation not stated Concealment of allocation: not stated Blinding: observer and outcome assessor blinded Follow‐up: mean 4.6 to 4.9 years Losses to follow‐up: not reported, but 3 participants in the treatment group died (none in the control group)
Participants	Country: Ontario, Canada No. of participants: 47 Age: mean age 61 years Sex: males 26; females 21 Inclusion criteria: asymptomatic postphlebitic syndrome and venous valvular incompetence (as assessed by photoplethysmography or venous Doppler) Exclusion criteria: previous graduated compression stocking therapy, geographic inaccessibility, and failure to provide informed consent
Interventions	Intervention group (n = 24): elastic compression stockings; below‐knee elastic compression stockings with ankle pressure of 20 to 30 mmHg at the ankle region Control (n = 23): placebo stocking Start of compression stockings: 1 year after DVT diagnosis
Outcomes	Cumulative incidence of PTS
Notes	Three‐part study; only data from study 2 are taken into account Study was terminated after an interim analysis owing to slow recruitment of patients.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No description of random sequence generation
Allocation concealment (selection bias)	Unclear risk	No description of allocation concealment
Blinding (performance bias and detection bias) Objective outcome(s)	Low risk	Participants and outcome assessors were blinded. For participants, placebo stockings were provided. Participants were informed not to wear stockings to the assessments.
Blinding (performance bias and detection bias) Subjective outcome(s)	Low risk	Participants and outcome assessors were blinded. For participants, placebo stockings were provided. Participants were informed not to wear stockings to the assessments. The definition of PTS contained both objective and subjective items.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Incomplete outcome data are not described, but 3 participants (in the active stocking group) died.
Selective reporting (reporting bias)	Low risk	Only PTS was a prespecified outcome; this is reported.
Other bias	Low risk	Study seems to be free of other risk of bias.