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Can clinical features distinguish between immobile patients with stroke at high and low risk of deep vein thrombosis? Statistical modelling based on the CLOTS trials cohorts
  1. Martin Dennis1,
  2. Peter Sandercock1,
  3. John Reid2,
  4. Catriona Graham3,
  5. Gordon Murray4,
  6. Graham Venables5,
  7. Anthony Rudd6,
  8. Gill Bowler7,
  9. The CLOTS Trials Collaboration
  1. 1Division of Clinical Neurosciences, University of Edinburgh, Western General Hospital, Edinburgh, UK
  2. 2Borders General Hospital, Melrose, UK
  3. 3Epidemiology and Statistics Core, Wellcome Trust Clinical Research Facility, University of Edinburgh Western General Hospital, Edinburgh, UK
  4. 4Centre for Population Health Sciences, The University of Edinburgh Medical School, Edinburgh, UK
  5. 5The Royal Hallamshire Hospital, Sheffield, UK
  6. 6North Wing, St Thomas' Hospital, London, UK
  7. 7Department of Procurement, Western General Hospital, Edinburgh, UK
  1. Correspondence to Professor Martin Dennis, Division of Clinical neurosciences, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK; martin.dennis{at}


Background Deep vein thrombosis (DVT) is an important complication of stroke. Guidelines recommend that DVT prophylaxis should be guided by an assessment of the individual patient's risk. The authors aimed to develop and test models to predict DVT risk.

Methods The Clots in Legs Or sTockings after Stroke (CLOTS) Trial 1 randomised 2518 immobile patients with acute stroke to thigh-length graduated compression stockings (GCS) or no GCS and CLOTS Trial 2 randomised 3114 to thigh-length or below-knee GCS. The authors collected potential predictive variables at baseline and detected DVTs with compression duplex ultrasound scans at about 7–10 days and 25–30 days. The authors developed models with logistic regression to predict DVT in 1242 Trial 2 patients who had two scans and tested the models in the 1422 Trial 1 patients with two scans by estimating the area under the receiver operating characteristic curve (AUC).

Results 168 (11.8%) patients in Trial 1 and 122 (9.8%) in Trial 2 had proximal DVTs. A model based on the Trial 2 cohort contained four of the 12 baseline variables: dependent before stroke (OR=3.62, 95% CI 2.15 to 6.08), unable to lift arms off bed (OR 1.89, 95% CI 1.23 to 2.90), history of DVT/pulmonary embolism (OR 3.69, 95% CI 1.98 to 6.88) and diabetes (OR 0.55, 95% CI 0.30 to 0.99). The AUC in the development cohort was 0.65 but only 0.57, 95% CI (0.53 to 0.61) in the Trial 1 cohort, indicating poor discrimination.

Conclusions Unfortunately, models based on clinical factors alone discriminate poorly between immobile patients with stroke at high and low risk, and would not facilitate individual tailoring of DVT prophylaxis strategies.

  • Stroke
  • deep vein thrombosis
  • prediction
  • complications
  • randomised trials
  • ultrasound

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  • See Editorial commentary, p 1063

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  • Funding The Clots in Legs or Stockings After Stroke Trials were funded by research grants from the Chief Scientist Office of the Scottish government, Chest Heart and Stroke Scotland and the Medical Research Council of the UK. The additional analytical work involved in this report was supported by the Stroke Complication and Outcomes Prediction Engine project funded by Chest Heart and Stroke Scotland. The CLOTS trial collaboration acknowledges the financial support of NHS Research Scotland (NRS), through the Scottish Stroke Research Network and of the Dept of Health, through the UK Stroke Research Network.

  • Competing interests Covidien, Mansfield, USA provided free supplies of their graduated compression stockings to hospitals participating in the trials.

  • Ethics approval Ethics approval was provided by the Multicentre Research Ethics Committees in Scotland and England, and the local ethics committees of all contributing centres approved the protocol.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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