Thigh-length versus below-knee stockings for deep venous thrombosis prophylaxis after stroke: a randomized trial

CLOTS Trial Collaborat

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140 Citations (Scopus)


Background: Graduated compression stockings are widely used for deep venous thrombosis (DVT) prophylaxis. Although below-knee stockings are used more often than thigh-length stockings, no reliable evidence indicates that they are as effective as thigh-length stockings.

Objective: To compare the effectiveness of thigh-length stockings with that of below-knee stockings for preventing proximal DVT in immobile, hospitalized patients with stroke.

Design: Parallel-group trial with centralized randomization (minimization within centers) to ensure allocation concealment. The ultrasonographers who looked for DVT were blinded, but the patients and caregivers were not. ( registration number: ISRCTN28163533)

Setting: 112 hospitals in 9 countries.

Patients: 3114 immobile patients hospitalized with acute stroke between January 2002 and May 2009.

Intervention: 1552 patients received thigh-length stockings and 1562 patients received below-knee stockings to wear while they were in the hospital.

Measurements: Ultrasonographers performed compression duplex ultrasonography in 1406 patients (96% of survivors) in each treatment group between 7 and 10 days after enrollment. They performed a second scan in 643 patients in the thigh-length stockings group and 639 in the below-knee stockings group at about 25 to 30 days. The primary outcome was symptomatic or asymptomatic DVT in the popliteal or femoral veins, detected on either scan.

Results: Patients were retained in their assigned group for all analyses. The primary outcome occurred in 98 patients (6.3%) who received thigh-length stockings and 138 (8.8%) who received below-knee stockings (absolute difference, 2.5 percentage points [95% CI, 0.7 to 4.4 percentage points]; P = 0.008), an odds reduction of 31% (CI, 9% to 47%). Seventy-five percent of patients in both groups wore the stockings for 30 days or until they were discharged, died, or regained mobility. Skin breaks occurred in 61 patients who received thigh-length stockings (3.9%) and 45 (2.9%) who received below-knee stockings.

Limitation: Blinding was incomplete, 2 scans were not obtained for all enrolled patients, and the trial was stopped before the target accrual was reached.

Conclusion: Proximal DVT occurs more often in patients with stroke who wear below-knee stockings than in those who wear thigh-length stockings.

Original languageEnglish
Pages (from-to)553-562
Number of pages10
JournalAnnals of Internal Medicine
Issue number9
Publication statusPublished - 2 Nov 2010


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