Ruud Oudega, MD; Arno W. Hoes, MD, PhD; Karel G.M. Moons, PhD
Grant Support: By the Healthcare Research Foundation “IJsselmond,” Zwolle, the Netherlands, and by The Netherlands Organization for Scientific Research (ZON-MW 917-46-360).
Potential Financial Conflicts of Interest: None disclosed.
Requests for Single Reprints: Ruud Oudega, MD, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, P.O. Box 85060, 3508 AB Utrecht, the Netherlands; e-mail, firstname.lastname@example.org.
Current Author Addresses: Drs. Oudega, Hoes, and Moons: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, P.O. Box 85060, 3508 AB Utrecht, The Netherlands.
Author Contributions: Conception and design: R. Oudega, A.W. Hoes, K.G.M. Moons.
Analysis and interpretation of the data: R. Oudega, A.W. Hoes, K.G.M. Moons.
Drafting of the article: R. Oudega, A.W. Hoes, K.G.M. Moons.
Critical revision of the article for important intellectual content: R. Oudega, A.W. Hoes, K.G.M. Moons.
Final approval of the article: R. Oudega, A.W. Hoes, K.G.M. Moons.
Provision of study materials or patients: R. Oudega.
Statistical expertise: K.G.M. Moons.
Collection and assembly of data: R. Oudega.
Using data from secondary care outpatients, Wells and colleagues developed a diagnostic rule to estimate the probability of the presence of deep venous thrombosis (DVT). The accuracy of the Wells rule has not been properly validated for use in primary care patients in whom DVT is suspected.
To validate the diagnostic accuracy of the Wells rule, with and without d-dimer testing, in a primary care setting.
Cross-sectional study with prospective data collection from 1 January 2002 to 1 March 2003.
110 primary care practices in a circumscribed geographic region in The Netherlands.
1295 consecutive patients who consulted their primary care physician about symptoms suggestive of DVT.
All patients underwent history-taking and physical examination to calculate the Wells rule score, and d-dimer testing. Repeated leg ultrasonography was the reference standard to determine the true presence or absence of DVT.
In the primary care setting, 12.0% of patients in the low-risk group had DVT; the original study by Wells and colleagues reported a rate of 3% among such patients. When combined with negative results on a d-dimer test, the Wells rule yielded a prevalence of DVT of 2.9% in the lowest-risk group, whereas the prevalence was 0.9% in the original study.
Patients with previous DVT were included, and the diagnostic reference standard was different from that used in Wells and colleagues' original study.
The Wells rule, alone or in combination with d-dimer testing, does not guarantee accurate estimation of risk in primary care patients in whom DVT is suspected.
Physicians sometimes use a 9-item clinical rule (the Wells rule) to assess probability of deep venous thrombosis (DVT). In the original study that developed the Wells rule, only 3% of patients who were classified as low risk by the rule had DVT.
A total of 110 primary care physicians assessed 1295 consecutive outpatients with symptoms suggestive of DVT and then referred them to hospitals for diagnosis with leg ultrasonography. Twelve percent of patients who were classified as low risk by the physicians' Wells rule assessments had DVT.
Low-risk categorization by the Wells rule may not safely rule out DVT in all primary care patients.
Table 1. The Wells Rule To Estimate the Probability of Deep Venous Thrombosis
Study protocol and outcome.d
Table 2. Patient Characteristics
Table 3. Diagnostic Performance of the Wells Rule
Table 4. Application of Different Thresholds of the Wells Score
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Ruud Oudega, Arno W. Hoes, Karel G.M. Moons. The Wells Rule Does Not Adequately Rule Out Deep Venous Thrombosis in Primary Care Patients. Ann Intern Med. 2005;143:100–107. doi: 10.7326/0003-4819-143-2-200507190-00008
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Published: Ann Intern Med. 2005;143(2):100-107.
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