What’s New in the Patient Safety World

October 2010


Graduated Compression Stockings: CLOTS Confuses Clinicians



Our What’s New in the Patient Safety World column for July 2009 “Unintended Consequences of a DVT Prevention Strategy” reported on a study (CLOTS trial 1) which showed that not only do thigh-high graduated stockings not prevent DVT in stroke patients, they actually cause harm. Skin breaks, ulcers, blisters, and skin necrosis were significantly more common in patients allocated to GCS than in those allocated to avoid their use.


Now the CLOTS Trial 2 has published its results and they absolutely confuse the issue! Clots Trial 2 compared thigh-length graduated compression stockings to below-knee stockings and found fewer cases of VTE with the thigh-length stockings. The study populations and protocols for the two trials were the same, though the sites differed. The CLOTS Trial 2 was discontinued early because of the results of CLOTS Trial 1 but had already reached its predetermined enrollment goal. Proximal DVT, the primary study outcome, had an absolute risk reduction in the thigh-length group of 2.5% and the relative risk reduction was 31%. There were no differences in distal DVT, pulmonary emboli or deaths between the 2 groups. There were more cases with skin problems in the thigh-length group but these were relatively mild.


The authors consider several possible explanations for the seemingly contradictory results of the 2 trials. One is that below-knee stockings might actually increase the risk for DVT in stroke patients. The other is that the first CLOTS trial may have underestimated a positive effect of the thigh-length stockings.


We concur with the accompanying editorial (Kearon 2010) that there remain significant uncertainties as to how to best prevent DVT in stroke patients. Moreover, these studies highlight the need for randomized controlled trials of graduated compression stockings in other patient populations since they are so widely used in other patient populations. Even in surgical patients, where graduated compression stockings have been shown in multiple studies to reduce the occurrence of VTE, there has been no comparison of thigh-length vs. below-knee stockings. And while guidelines generally recommend use of thigh-length stockings, below-knee stockings are probably used more frequently in actual practice.



So in stroke patients, where concerns about use of pharmacologic VTE prophylaxis remain, we currently still don’t have strong evidence to support the use of graduated compression stockings as a mechanical alternative. We will have to await the results of the CLOTS Trial-3, which is looking at both the efficacy and safety of pneumatic compression stockings in stroke patients.







The CLOTS Trials Collaboration. Effectiveness of thigh-length graduated compression stockings to reduce the risk of deep vein thrombosis after stroke (CLOTS trial 1): a multicentre, randomised controlled trial. The Lancet 2009; 373:1958 - 1965, 6 June 2009




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. Annals of Internal Medicine 2010. Published early on line September 21, 2010




Kearon C, O'Donnell M. (Editorial). Should Patients With Stroke Wear Compression Stockings to Prevent Venous Thromboembolism? Annals of Internal Medicine 2010. Published early on line September 21, 2010
















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