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Summaries for Patients are a service provided by Annals to help patients better understand the complicated and often mystifying language of modern medicine.
Doctors use several strategies to diagnose DVT, including a scan that uses sound waves to look at clotting in the veins (ultrasonography) and blood tests (d-dimer tests) that help measure whether a clot has formed and is breaking down. Doctors may repeat ultrasonography within 1 week if the initial scan is negative. To decide when to do these tests, doctors often assess a patient's medical background, symptoms, and physical examination. They sometimes sum the presence or absence of 9 items (the Wells rule) to help sort patients into low, moderate, or high probability of having DVT. For example, in the original study that developed the Wells' rule, only 3% of patients who were classified as low risk by the rule had DVT. Few additional studies document how well the Wells rule places people into a low-risk group.
SUMMARIES FOR PATIENTS
Estimating the Probability of Deep Venous Thrombosis in Outpatients
19 July 2005 | Volume 143 Issue 2 | Page I-27
Summaries for Patients are presented for informational purposes only. These summaries are not a substitute for advice from your own medical provider. If you have questions about this material, or need medical advice about your own health or situation, please contact your physician. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the American College of Physicians.
The summary below is from the full report titled "The Wells Rule Does Not Adequately Rule Out Deep Venous Thrombosis in Primary Care Patients." It is in the 19 July 2005 issue of Annals of Internal Medicine (volume 143, pages 100-107). The authors are R. Oudega, A.W. Hoes, and K.G.M. Moons.
What is the problem and what is known about it so far?
Deep venous thrombosis (DVT) occurs when blood clots form in the large veins of the legs. Pieces of the clots can break off and travel through the bloodstream to the lungs. The clots can cause serious symptoms and even death if they are not diagnosed and treated quickly. Because people with DVT are treated with blood-thinning medicines that can cause serious bleeding, accurate diagnosis is very important.
Why did the researchers do this particular study?
To see how well the Wells rule classifies outpatients with suspected DVT into a low-risk group.
Who was studied?
1295 adults with suspected DVT seen in 110 primary care practices in the Netherlands. Their average age was 60 years, and 36% were men.
How was the study done?
One hundred ten primary care physicians examined 1295 outpatients with symptoms suggestive of DVT. After completing standard study forms that included the Wells rule, they referred patients to hospitals for D-dimer tests and leg ultrasonography. Patients with normal ultrasounds had repeated ultrasonography 7 days later. The person who did the ultrasonography did not know the results of patients' history, physical examination, or D-dimer test. The researchers then assessed how often DVT was diagnosed by ultrasonography in patients who had been classified as low risk by their scores on the Wells rule. They also assessed how often DVT was diagnosed in patients with low-risk Wells scores and normal D-dimer results.
What did the researchers find?
Approximately 12% of patients who were classified as low risk by physicians' Wells rule assessments had DVT. About 3% of patients with low-risk scores on the Wells rule and normal D-dimer results had DVT.
What were the limitations of the study?
The study used a different method to diagnose DVT than did the original Wells study; it also included patients with previous DVT, while the original Wells study excluded them. Patients with previous DVT have high risks for repeated DVT.
What are the implications of the study?
Low scores on the Wells rule do not safely guarantee low probability of DVT in all outpatients with suspected leg clots.
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This article has been cited by other articles:
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  D. Toll, R Oudega, Y Vergouwe, K. Moons, and A. Hoes A new diagnostic rule for deep vein thrombosis: safety and efficiency in clinically relevant subgroups Fam. Pract., February 1, 2008; 25(1): 3 - 8. [Abstract] [Full Text] [PDF]
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 A. Qaseem, V. Snow, P. Barry, E. R. Hornbake, J. E. Rodnick, T. Tobolic, B. Ireland, J. B. Segal, E. B. Bass, K. B. Weiss, et al. Current Diagnosis of Venous Thromboembolism in Primary Care: A Clinical Practice Guideline from the American Academy of Family Physicians and the American College of Physicians Ann Intern Med, March 20, 2007; 146(6): 454 - 458. [Abstract] [Full Text] [PDF]
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 A. Qaseem, V. Snow, P. Barry, E. R. Hornbake, J. E. Rodnick, T. Tobolic, B. Ireland, J. Segal, E. Bass, K. B. Weiss, et al. Current Diagnosis of Venous Thromboembolism in Primary Care: A Clinical Practice Guideline from the American Academy of Family Physicians and the American College of Physicians Ann. Fam. Med, January 1, 2007; 5(1): 57 - 62. [Abstract] [Full Text] [PDF]
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 S. M Stevens and W. Ageno The Wells rule was not useful in ruling out deep venous thrombosis in a primary care setting Evid. Based Med., April 1, 2006; 11(2): 57 - 57. [Full Text] [PDF]
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 P. S. Wells, C. Owen, S. Doucette, D. Fergusson, and H. Tran Does This Patient Have Deep Vein Thrombosis? JAMA, January 11, 2006; 295(2): 199 - 207. [Abstract] [Full Text] [PDF]
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 Ruling Out DVT Journal Watch Cardiology, September 9, 2005; 2005(909): 7 - 7. [Full Text]
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 Validation of the Wells Score for Predicting DVT Journal Watch Emergency Medicine, August 23, 2005; 2005(823): 4 - 4. [Full Text]
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 Ruling Out DVT Journal Watch (General), August 12, 2005; 2005(812): 5 - 5. [Full Text]
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 A. Tonks What's new in the other general journals BMJ, July 30, 2005; 331(7511): 257 - 258. [Full Text] [PDF]
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J. D. Douketis Use of a Clinical Prediction Score in Patients with Suspected Deep Venous Thrombosis: Two Steps Forward, One Step Back? Ann Intern Med, July 19, 2005; 143(2): 140 - 142. [Full Text] [PDF]
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