The CLOTS (Clots in Legs Or sTockings after Stroke) Trial Collaboration
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.
To compare the effectiveness of thigh-length stockings with that of below-knee stockings for preventing proximal DVT in immobile, hospitalized patients with stroke.
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. (Controlled-trials.com registration number: ISRCTN28163533)
112 hospitals in 9 countries.
3114 immobile patients hospitalized with acute stroke between January 2002 and May 2009.
1552 patients received thigh-length stockings and 1562 patients received below-knee stockings to wear while they were in the hospital.
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.
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.
Blinding was incomplete, 2 scans were not obtained for all enrolled patients, and the trial was stopped before the target accrual was reached.
Proximal DVT occurs more often in patients with stroke who wear below-knee stockings than in those who wear thigh-length stockings.
Medical Research Council of the United Kingdom, Chief Scientist Office of the Scottish Government, and Chest Heart and Stroke Scotland.
Are either thigh-length or below-knee stockings better for reducing risk for deep venous thrombosis (DVT) in patients with stroke?
This large randomized trial involved immobile patients with acute stroke. Patients had ultrasonography 7 to 10 days after hospitalization and then again 15 to 20 days after that. Proximal DVT was detected in 6.3% and 8.8% of those who received thigh-length or below-knee stockings, respectively. Skin breaks occurred in 3.9% of those who received thigh-length stockings and 2.9% of those who received below-knee stockings.
Not all patients had both ultrasonography scans.
Proximal DVT occurs more commonly with below-knee stockings than with thigh-length stockings in immobile patients with stroke.
We coded the reason why a scan was not performed; however, if a patient was not scheduled for a scan but died, then that death would not be recorded here. Therefore, the numbers of deaths are not the same as those in Tables 2 and 3. CLOTS = Clots in Legs Or sTockings after Stroke.
Odds ratios less than 1 correspond to a reduction in the primary outcome with thigh-length stockings. P values are for the interaction between the treatment effect and the subgroup. We excluded patients without previous deep venous thrombosis who died and those who did not have compression duplex ultrasonography from the denominators, which therefore differ from the total number allocated to each treatment group.
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The CLOTS (Clots in Legs Or sTockings after Stroke) Trial Collaboration. Thigh-Length Versus Below-Knee Stockings for Deep Venous Thrombosis Prophylaxis After Stroke: A Randomized Trial. Ann Intern Med. 2010;153:553-562. doi: 10.7326/0003-4819-153-9-201011020-00280
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Published: Ann Intern Med. 2010;153(9):553-562.
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