Accuracy of clinical assessment of deep-vein thrombosis

Deep-vein thrombosis

Deep-vein thrombosis is an important complication of several inherited and acquired disorders, but may also occur spontaneously. Prevention of recurrent venous thrombosis and pulmonary embolism is the main reason for accurate diagnosis and adequate treatment. This seminar discusses only symptomatic deep-vein thrombosis. The diagnosis can be confirmed by objective tests in only about 30% of patients with symptoms. Venous thromboembolic complications happen in less than 1% of untreated patients in whom the presence of venous thrombosis is rejected on the basis of serial ultrasonography or ultrasonography plus either D-dimer or clinical score. Initial anticoagulant treatment (intravenous or subcutaneous heparin) should continue until oral anticoagulant treatment, started concurrently, increases the international normalised ratio above 2.0 for more than 24 h. The optimum duration of oral anticoagulant treatment is unresolved, but may be guided by the presence of temporary or persistent risk factors or presentation with recurrent venous thromboembolism.

Non-invasive diagnosis of venous thromboembolism in outpatients

BACKGROUND

We designed a simple and integrated diagnostic algorithm for acute venous thromboembolism based on clinical probability assessment of deep-vein thrombosis (DVT) or pulmonary embolism (PE), plasma D-dimer measurement, lower-limb venous compression ultrasonography, and lung scan to reduce the need for phlebography and pulmonary angiography.

METHODS

918 consecutive patients presenting at the emergency ward of the Geneva University Hospital, Geneva, Switzerland, and Hôpital Saint-Luc, Montreal, Canada, with clinically suspected venous thromboembolism were entered into a sequential diagnostic protocol. Patients in whom venous thromboembolism was deemed absent were not given anticoagulants and were followed up for 3 months.

FINDINGS

A normal D-dimer concentration (<500 microg/L by a rapid ELISA) ruled out venous thromboembolism in 286 (31%) members of the study cohort, whereas DVT by ultrasonography established the diagnosis in 157 (17%). Lung scan was diagnostic in 80 (9%) of the remaining patients. Venous thromboembolism was also deemed absent in patients with low to intermediate clinical probability of DVT and a normal venous ultrasonography (236 [26%] patients), and in patients with a low clinical probability of PE and a non-diagnostic result on lung scan (107 [12%] patients). Pulmonary angiography and phlebography were done in only 50 (5%) and 2 (<1%) of the patients, respectively. Hence, a non-invasive diagnosis was possible in 866 (94%) members of the entire cohort. The 3-month thromboembolic risk in patients not given anticoagulants, based on the results of the diagnostic protocol, was 1.8% (95% CI 0.9-3.1).

INTERPRETATION

A diagnostic strategy combining clinical assessment, D-dimer, ultrasonography, and lung scan gave a non-invasive diagnosis in the vast majority of outpatients with suspected venous thromboembolism, and appeared to be safe.

Dalteparin in emergency patients to prevent admission prior to investigation for venous thromboembolism

A 15-month prospective cohort study of emergency department (ED) patients with suspected venous thromboembolism was conducted to assess the role of low molecular weight heparin (dalteparin) in an emergency setting in suspected venous thromboembolism prior to diagnostic confirmation. Patients were given a therapeutic dose of dalteparin and were discharged home; they then returned the next day for diagnostic testing. All patients were followed for 3 months. Of 128 patients, 44 had positive test results and 84 had negative test results. Four patients required admission for other reasons. Seventeen had continuing symptoms after initial negative testing; 10 returned to the ED and 9 had repeat Doppler ultrasound, all of which remained negative. None of the 84 negative patients were diagnosed with venous thromboembolism subsequent to an initial negative test. There were no serious adverse effects. This study suggests that treatment with low molecular weight heparin pending outpatient investigation for suspected venous thromboembolism in emergency patients is safe and effective. This could lead to substantial cost savings in the management of this problem. Further study is warranted.

D-dimer testing as an adjunct to ultrasonography in patients with clinically suspected deep vein thrombosis: prospective cohort study. The Multicentre Italian D-dimer Ultrasound Study Investigators Group

OBJECTIVE

To investigate the efficacy of using a rapid plasma D-dimer test as an adjunct to compression ultrasound for diagnosing clinically suspected deep vein thrombosis.

DESIGN

D-dimer concentrations were determined in all patients with a normal ultrasonogram at presentation. Repeat ultrasonography was performed 1 week later only in patients with abnormal D-dimer test results.

MAIN OUTCOME AND MEASURES

Patients with normal ultrasonograms were not treated with anticoagulants and were followed for 3 months for thromboembolic complications.

SETTING

University research and affiliated centres.

SUBJECTS

946 patients with clinically suspected deep vein thrombosis.

RESULTS

Ultrasonograms were abnormal at presentation in 260 (27.5%) patients. Of the remaining 686 patients tested for D-dimer, 88 (12.8%) had abnormal concentrations. During follow up venous thromboembolic complications occurred in one of the 598 patients who were not treated with anticoagulants and who had an initial normal ultrasonogram and D-dimer concentration, whereas thromboembolic complications occurred in two of the 83 untreated patients who had abnormal D-dimer concentrations but a normal repeat ultrasonogram. The cumulative incidence of venous thromboembolic complications during follow up was 0.4% (95% confidence interval 0% to 0.9%). The rapid plasma D-dimer test used as an adjunct to compression ultrasonography resulted in a reduction in the mean number of repeat ultrasound examinations and additional hospital visits from 0.7 to 0.1 per patient.

CONCLUSIONS

Testing for D-dimer as an adjunct to a normal baseline ultrasound examination decreased the number of subsequent ultrasound examinations considerably without any increased risk of venous thromboembolic complications in patients not receiving anticoagulants. The use of ultrasound and testing for D-dimer enabled treatment decisions to be made at the time of presentation in most patients.

Laboratory diagnosis of venous thromboembolism

Venous thromboembolism is a common medical condition in both out-patients and in-patients. Despite the development of non-invasive tests, the diagnosis of deep vein thrombosis and pulmonary embolism remains a clinical challenge. In an effort to improve diagnostic accuracy and to reduce the necessity of serial testing, laboratory markers of thrombin generation and fibrinolysis have been investigated as first-line screening tests. Although the majority of markers are elevated in acute thrombosis, D-dimer, a specific derivative of cross-linked fibrin, appears to have the most potential clinical utility. Accuracy studies and preliminary management trials suggest that rapid D-dimer enzyme-linked immunosorbent assays and the whole blood agglutination assay, SimpliRED D-dimer (Agen Biomedical, Brisbane, Australia), have strong potential as exclusionary tests in patients with suspected venous thrombosis.

Diagnostic management of venous thromboembolism

The accuracy of diagnostic methods for the diagnosis of deep vein thrombosis and pulmonary embolism in symptomatic patients is critically reviewed. In addition, the safety of withholding anticoagulant therapy from patients with suspected deep vein thrombosis or pulmonary embolism in whom the qualified diagnostic strategy was normal is evaluated by determining the frequency of venous thromboembolic complications during 3 months of follow-up. It is shown that the currently used available diagnostic techniques for deep vein thrombosis are all able to identify the majority of patients who indeed have venous thrombosis. However, as result of its accuracy and practical advantages, compression ultrasound is the test of choice in the evaluation of symptomatic patients. Patients with a normal test outcome should be re-tested to detect the small proportion of patients with proximally extending calf vein thrombosis. In the strategy of repeated diagnostic testing, impedance plethysmography could be used as an alternative to ultrasonography. To obtain a reduction in repeat tests various diagnostic strategies have been evaluated and it was shown that these strategies, using non-invasive tests, can be as accurate and safe as the invasive reference strategy. The safeties of the various strategies were very similar; however, important differences were observed with respect to the practical implementation of the various diagnostic strategies. Simplification of the repeated testing strategy by using a D-dimer assay and/or a clinical decision rule seems to be promising. The reference standard for the diagnosis of pulmonary embolism remains pulmonary angiography. Several strategies based on non-invasive diagnostic methods have been evaluated for their safety and complexability. Perfusion-ventilation lung scanning is the most thoroughly evaluated non-invasive technique so far. It seems safe to withhold anticoagulant therapy in patients suspected of pulmonary embolism with a normal perfusion lung scan result; however, further testing is needed in the case of a non-diagnostic perfusion-ventilation lung scan result. At this moment angiography is the method of choice in this category of patients. D-dimer assays, clinical decision rules and ultrasound examinations of the legs seem to have a high potential to limit the need for angiography. Also, spiral computerized tomography and magnetic resonance imaging are promising techniques, but their role in the diagnostic management of pulmonary embolism is still uncertain.

Thromboprophylaxis in hip arthroplasty. New frontiers and future strategy

Coagulation-related complications are a frequent cause of death following hip replacement surgery. Venographically-proven deep vein thrombosis (DVT) is found in a high frequency. Most cases have no symptoms. Fatal pulmonary embolism (PE) may develop from subclinical thrombi. In addition, arterial thromboses may induce serious cardiovascular events and an unknown number of patients may develop cardiorespiratory insufficiency, due to non-fatal venous PE. Finally, several patients may develop venous insufficiency. Recent prospective double-blind studies have shown that the frequency of deep vein thrombosis increased after hospital discharge in patients undergoing hip replacement surgery. Prolonged thrombo-prophylaxis with low-molecular-weight heparin (dalteparin or enoxaparin) is recommended for at least 5 weeks after the operation.

New approaches to the delivery of anticoagulant services

Anticoagulant services are changing in response to the increasing demands on the service. New approaches to the delivery of the service are evolving with more local delivery of services and a shift in the service from secondary to primary care. This change has been assisted by the development of near patient testing devices and the use of computerized anticoagulant decision support systems that are increasingly used in both secondary and primary care. The evolving role of the clinical nurse/pharmacist in the provision of this service is an important development enabling more rapid discharge of patients and the provision of local delivery of service.

Diagnosis of deep venous thrombosis and pulmonary embolism

Diagnostic evaluation in the patient with suspected deep vein thrombosis (DVT) and pulmonary embolism (PE) includes a clear correlation between clinical probability, test selection and test interpretation. Real-time B-mode ultrasound with color Doppler remains the imaging technique of choice in suspected DVT. The ventilation/perfusion (V/Q) lung scan is the preferred diagnostic modality in suspected PE. The D-dimer assay may be useful in excluding PA. New diagnostic techniques, including spiral computerized tomography may further modify the diagnostic algorithm.

Venous thromboembolic disease

The advent of spiral CT has encouraged investigation into the diagnosis of venous thromboembolic disease. It has also exposed the limitations of prior methods of investigation and raised questions as to the significance of small pulmonary emboli. This article discusses this new technique, the clinical detection of venous thromboembolic disease and possible current and future strategies in diagnosis.

A simple clinical model for the diagnosis of deep-vein thrombosis combined with impedance plethysmography: potential for an improvement in the diagnostic process

OBJECTIVES

We recently demonstrated the utility of a clinical model combined with ultrasonography to assist the diagnostic approach in patients with suspected deep-vein thrombosis (DVT). In this study we also sought to demonstrate that the model is useful with impedance plethysmography, a less accurate and less utilized diagnostic test. The original clinical model is slightly cumbersome to use; thus at the completion of the study we attempted to develop a simpler scoring system with a goal of maintaining accuracy.

DESIGN

An open, nonrandomized, multicentre trial.

SETTING

Three centres, two in Canada, and one in Italy.

SUBJECTS

Ambulatory patients with suspected deep-vein thrombosis.

INTERVENTIONS

All patients were assessed clinically to determine the probability for deep-vein thrombosis prior to performing impedance plethysmography and venography. We compared the accuracy of impedance plethysmography between the three pretest probability categories of high, moderate and low. All of the above were performed and interpreted by independent observers. When the study was completed, we revised the clinical model by first performing a simple regression analysis then a multiple logistic regression analysis; a scoring system was devised using the latter.

RESULTS

Impedance plethysmography is significantly more sensitive and less specific for all DVT in patients with high pretest probability for deep-vein thrombosis (P = 0.001). The post- test probability (positive predictive value) for deep-vein thrombosis with an abnormal impedance plethysmography result was significantly different (P = 0.0001) between the three pretest probability categories. Multiple regression analysis has provided a new model with only nine variables and a simple scoring system. The retrospective application of the revised clinical model, which is simpler to use, suggests it will provide similar results as the original clinical model when combined with impedance plethysmography. The combination of impedance plethysmography and the clinical model suggests patients are likely to have false positive results if they have a low or moderate pretest probability for deep-vein thrombosis and false negative results if the pretest probability is high. The combination of a low pretest probability and a normal impedance plethysmography result may exclude the need for serial testing, and represented more than 50% of our patient population.

CONCLUSIONS

The use of the clinical model in conjunction with impedance plethysmography would decrease the number of false positive and negative diagnoses and could markedly decrease the need for serial impedance plethysmography. Combining the clinical model with impedance plethysmography could overcome the fact that impedance plethysmography is clearly less accurate than venous ultrasound imaging. The use of the revised clinical model may increase acceptability and utility, but prospective testing is required before widespread use.

Value of assessment of pretest probability of deep-vein thrombosis in clinical management

BACKGROUND

When ultrasonography is used to investigate deep-vein thrombosis, serial testing is recommended for those who test negative initially. Serial testing is inconvenient for patients and costly. We aimed to assess whether the calculation of pretest probability of deep-vein thrombosis, with a simple clinical model, could be used to improve the management of patients who present with suspected deep-vein thrombosis.

METHODS

Consecutive outpatients with suspected deep-vein thrombosis had their pretest probability calculated with a clinical model. They then underwent compression ultrasound imaging of proximal veins of the legs. Patients at low pretest probability underwent a single ultrasound test. A negative ultrasound excluded the diagnosis of deep-vein thrombosis whereas a positive ultrasound was confirmed by venography. Patients at moderate pretest probability with a positive ultrasound were treated for deep-vein thrombosis whereas patients with an initial negative ultrasound underwent a single follow-up ultrasound 1 week later. Patients at high pretest probability with a positive ultrasound were treated whereas those with negative ultrasound underwent venography. All patients were followed up for 3 months for thromboembolic complications.

FINDINGS

95 (16.0%) of all 593 patients had deep-vein thrombosis; 3%, 17%, and 75% of the patients with low, moderate, and high pretest probability, respectively, had deep-vein thrombosis. Ten of 329 patients with low pretest probability had the diagnosis confirmed, nine at initial testing and one at follow-up. 32 of 193 patients with moderate pretest probability had deep-vein thrombosis, three diagnosed by the serial (1 week) test, and two during follow-up. 53 of 71 patients with high pretest probability had deep-vein thrombosis (49 by the initial ultrasound and four by venography). Only three (0.6%) of all 501 (95% CI 0.1-1.8) patients diagnosed as not having deep-vein thrombosis had events during the 3-month follow-up. Overall only 33 (5.6%) of 593 patients required venography and serial testing was limited to 166 (28%) of 593 patients.

INTERPRETATION

Management of patients with suspected deep-vein thrombosis based on clinical probability and ultrasound of the proximal deep veins is safe and feasible. Our strategy reduced the need for serial ultrasound testing and reduced the rate of false-negative or false-positive ultrasound studies.

Accuracy of two newly described D-dimer tests in patients with suspected deep venous thrombosis

Accumulating evidence suggests that the ELISA determination of D-Dimer might be a useful tool for the exclusion of deep vein thrombosis (DVT) of lower extremities, because of its high sensitivity and negative predictive value. However, conventional ELISA assay is time-consuming and, therefore, is not suitable for emergency use. To evaluate the accuracy of two rapid assays recently described, 126 consecutive outpatients with the clinical suspicion of DVT underwent the NycoCard D-Dimer and the Instant I.A. D-Dimer determination, using venography as the reference test. In all patients, the conventional ELISA assay was also performed. Venography confirmed the presence of DVT in 30 patients (23.8%), and ruled out the diagnosis in the remaining 96. Instant I.A D-Dimer was positive in 28 patients with DVT (sensitivity, 93.3%), and negative in 90 subjects free from thrombosis (specificity, 93.8%). Nycocard D-Dimer correctly identified 27 patients with DVT (sensitivity 90.0%), and was negative in 77 subjects free from thrombosis (specificity, 80.2%). Sensitivity, specificity, negative and positive predictive values of both tests did not differ from those found with the classic ELISA method. In conclusion, both Instant I.A. D-Dimer and Nycocard D-Dimer assays show a great potential for clinical use.

Predictive power of clinical symptoms in patients with presumptive deep venous thrombosis

The predictive power of clinical symptoms in the diagnosis of deep venous thrombosis (DVT) was assessed using a retrospective design. The sample consisted of 61 rehabilitation patients who were referred for Doppler ultrasonography. Patients had a mean age of 60.6 (standard deviation, 18.4) years. Clinical measures documenting presence of swelling, warmth, fever, and lower limb asymmetry (> 2.5 cm) were correlated with the outcome of venous duplex Doppler examinations. Clinical symptoms had low sensitivity (0.07-0.33) but generally higher specificity (0.76-0.85) for DVT. Positive predictive power was lowest for fever (0.08) and highest for swelling (0.66). Prevalence rates for DVT were greatest (0.41) in patients presenting with multiple symptoms. Results suggest clinical predictors of DVT remain elusive. A high rate of false-positives based on clinical findings from examination is acceptable given the low risk associated with ultrasonography and the clear benefit of early diagnosis of DVT.

[Lines of conduct for training of physicians in echography and vascular Doppler and realization of vascular ultrasonic tests]

Vascular tests with duplex scanning have an important lace in the diagnostic and therapeutic strategy in vascular medicine; they are integrated by the physician within the strategy of pathology support. The realization and interpretation of vascular duplex scanning are subject to recommendations. The training of physicians takes into account the clinical context due to the fact that all aspects of these examinations are inseparable. Besides the theoretical education, it is important to be thorough in practical training. The realization of a minimal number of 250 examinations is advised, distributed among different sectors of anatomy and pathology. The acquiring and preservation of technical skills and the ability to provise solutions, requires the realization of additional 250 examinations. This total amount of 500 examinations is integrated into a global 2 year educational program. The preservation of skills requires 500 annual examinations. The training center is placed under the responsibility of a clinical physician, recognized in vascular medicine. This center must perform more than 2,000 examinations a year. Various centers can associate their abilities in order to ensure a complete training program.

Serial duplex ultrasound examinations for deep vein thrombosis in patients with suspected pulmonary embolism

PURPOSE

We have prospectively evaluated the need for serial venous duplex ultrasound examinations in an inpatient population with an initially normal study result.

METHODS

Patients were selected for study on the basis of clinical suspicion of pulmonary embolism and possible lower extremity deep vein thrombosis, a comorbid condition contributing to a nondiagnostic ventilation/perfusion lung scan, and an initially normal bilateral venous duplex ultrasound examination that included complete evaluation of the femoropopliteal system and the deep calf veins. Repeat duplex examinations were done during the same hospital admission between 5 and 14 days after the initial study.

RESULTS

Ninety-four patients with an initially normal duplex ultrasound examination result had repeat studies done at an average of 7.9 +/- 2.6 days. Ninety-two examination results remained normal bilaterally. Two patients had isolated intramuscular calf vein deep vein thrombosis: one in the gastrocnemius system of both calves with associated calf tenderness at 11-day follow-up and one in a mid-calf soleal vein without associated symptoms at 10 days. No patients had any evidence of deep vein thrombosis in the femoropopliteal or tibioperoneal venous systems.

CONCLUSIONS

Serial follow-up duplex ultrasound evaluation is unnecessary after an initially complete, normal study in patients with symptoms who have suspected pulmonary embolism and nondiagnostic ventilation-perfusion lung scans.

Appropriate indications for venous duplex ultrasonographic examinations

BACKGROUND

Because of the rapid growth in requests for lower extremity venous duplex ultrasonographic examinations, we have evaluated test results to determine the appropriate indications for testing and whether there is overuse of this technique.

METHODS

We reviewed the records of all patients who had duplex ultrasonogram during an 18-month period to rule out deep vein thrombosis (DVT). Test outcome was evaluated with data on the age, gender, outpatient or inpatient status, duration of symptoms, physical findings, and risk factors of the patients.

RESULTS

We reviewed 3474 examinations; 1265 outpatients and 1231 inpatients were evaluated to rule out DVT, and 978 patients were evaluated to rule out a source of pulmonary embolism. More outpatients were female, and they tended to be younger; outpatients also had more acute femoropopliteal DVT. The presence of sudden onset of unilateral swelling was a strong predictor of acute DVT in all three groups: 52% of such patients were found to have DVT. Mild unilateral symptoms with a coexistent risk factor was associated with a 10% to 20% prevalence of acute DVT. Chronic unilateral swelling was associated with acute DVT only with a coexistent risk factor and only in 1% of such patients. Bilateral swelling was only associated with acute DVT in the inpatient population, with 17% of studies having positive results. If calf tenderness was the only symptom with no associated risk factors, seven (1.6%) of 415 patients had acute DVT and six of these were tibioperoneal. No patients with cellulitis or isolated joint pain had acute DVT. With clinically suspected pulmonary embolism in patients without associated symptoms or risk factors, 7 (1.5%) of 447 studies showed tibioperoneal disease with no acute femoropopliteal disease.

CONCLUSIONS

The physical examination and clinical history of the patient remain important indicators of the presence (or absence) of lower extremity DVT and can guide the appropriate use of duplex ultrasonography for the diagnosis.

Diagnosis of deep vein thrombosis

Deep vein thrombosis (DVT) is an important, treatable disease that can be diagnosed by noninvasive imaging procedures. Ultrasound is the most accurate and readily available of these modalities but it still has limitations. False positive results occur in up 6% of patients, and calf DVT is not readily detected; thus serial ultrasonography is recommended in order to detect extension of a calf DVT. However, this results in many patients needlessly returning for a repeat assessment. A recently developed clinical model has the potential to identify false positive ultrasound results and to select patients who do not require serial testing. Certain rapidly performed D-dimer assays have similar potential but have not been evaluated in management strategies. In the subgroup of patients with suspected recurrent DVT and asymptomatic patients at high risk for DVT, ultrasonography and impedance plethysmography are less accurate, however, the clinical implications of this are unknown.