Elsevier

Thrombosis Research

Volume 123, Issue 4, February 2009, Pages 612-616
Thrombosis Research

Regular Article
Clinical probability assessment and D-dimer determination in patients with suspected deep vein thrombosis, a prospective multicenter management study

https://doi.org/10.1016/j.thromres.2008.04.007Get rights and content

Abstract

Objectives

To investigate the reliability of a combined strategy of clinical assessment score followed by a local D-dimer test to exclude deep vein thrombosis. For comparison D-dimer was analysed post hoc and batchwise at a coagulation laboratory.

Design

Prospective multicenter management study.

Setting

Seven hospitals in southern Sweden.

Subjects

357 patients with a suspected first episode of deep vein thrombosis (DVT) were prospectively recruited and pre-test probability score (Wells score) was estimated by the emergency physician. If categorized as low pre-test probability, D-dimer was analysed and if negative, DVT was considered to be ruled out. The primary outcome was recurrent venous thromboembolism (VTE) during 3 months of follow up.

Results

Prevalence of DVT was 23.5% (84/357). A low pre-test probability and a negative D-dimer result at inclusion was found in 31% (110/357) of the patients of whom one (0.9%, [95% CI 0.02–4.96]) had a VTE at follow up. Sensitivity, specificity, negative predictive value and negative likelihood ratio for our local D-dimer test in the low probability group were 85.7%, 74.5%, 98.2%, and 0,19 respectively compared to 85.6%, 67,6%, 97.9% and 0,23 using batchwise analysis at a coagulation laboratory.

Conclusion

Pre-test probability score and D-dimer safely rule out DVT in about 30% of outpatients with a suspected first episode of DVT. One out of 110 patients was diagnosed with DVT during follow up. No significant difference in diagnostic performance was seen between local D-dimer test and the post hoc batch analysis with the same reagent in the low probability group.

Introduction

Although patients with suspected deep vein thrombosis are common in hospital emergency departments, relatively few actually have deep vein thrombosis (DVT) [1], [2]. In recent years, new diagnostic methods involving assessment of clinical probability and the use of D-dimer analysis have proven safe and have simplified the diagnostic strategy of these patients [3], [4]. Recent studies have shown that low clinical probability and a negative D-dimer result exclude DVT in 30–50% of outpatients with suspected deep vein thrombosis and safely obviate the need for further diagnostic testing [5], [6].

According to Bayes' theorem the probability that a patient has the disease following diagnostic testing is determined by the estimated probability prior to the test (pretest probability) and the accuracy of the test [7]. In Scandinavia several studies indicate a higher prevalence (30–50%) of confirmed DVT in outpatients than observed in many other countries [8], [9], [10]. This would of course affect the PTP and increase the risk for false negative results and decrease the diagnostic exclusion rate. Furthermore, since D-dimer assays are not standardized and actually measure different products of the fibrin degradation the performance varies substantially between assays and populations [11], [12]. Because of these limitations many clinicians hesitate to implement this diagnostic strategy.

The purpose of this study was to examine whether a combined strategy of a clinical assessment score done in the emergency ward followed by a local D-dimer test was safe for the patients in a clinical setting where the prevalence of DVT in outpatients was high. We also wanted to address the question of whether D-dimer methods used locally were as reliable as the same method used in batch analysis under optimal circumstances with reduced variability from inter-assay differences.

Section snippets

Study design and patients

This study was performed between December 2003 and December 2005. Adult patients with a suspected first episode of DVT were potentially eligible for inclusion. Seven centres in southern Sweden, serving approximately 1 million residents, participated in the study. A total of 491 outpatients were consecutively evaluated for the study over the 2-year recruitment period. Patients were either self-referred, referred from primary care physicians or to a lesser extent sent in from other clinics. The

Results

Three hundred and fifty- seven patients were considered eligible and entered the study. The prevalence of DVT (final diagnosis) was 23.5% (84/357) of which 52 (63%) were considered proximal DVTs (proximal thrombosis if the thrombus was located in the popliteal or more proximal veins). The median age was 62 years and 138 (39%) were men. Other patient characteristics are shown in Table 2. Of the 357 patients entering the study, 159 (45%) were categorized as having a low, 141 (39%) intermediate,

Discussion

Assessment of clinical pre-probability scores and the use of D-dimer testing has simplified the diagnostic strategies for DVT and reduced the need for diagnostic imaging. Implementing these strategies into the diagnostic workup lowers costs [18], reduces inconvenient for the patients and is timesaving for both staff and patients at the emergency departments.

In this study we demonstrate that anticoagulation therapy can be safely withheld in almost 1/3 of outpatients with suspected DVT by using a

Acknowledgements

The SCORE Trial Study Group consists of the following investigators. The institutions are Departments of Internal Medicine: Lund University Hospital: J. Elf, C-G. Olsson; Helsingborg Hospital: J. Forsblad; Växjö Hospital: K-Å. Jönsson; Halmstad Hospital: C. Lagerstedt; Ystad Hospital: B. Löwgren; University Hospital of Malmö: P. Svensson; Kristianstad Hospital: I. Torstensson.

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