Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Objective testing for DVT is crucial because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. This guideline focuses on the identification of optimal strategies for the diagnosis of DVT in ambulatory adults.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that clinical assessment of pretest probability of DVT, rather than performing the same tests in all patients, should guide the diagnostic process for a first lower extremity DVT (Grade 2B). In patients with a low pretest probability of first lower extremity DVT, we recommend initial testing with D-dimer or ultrasound (US) of the proximal veins over no diagnostic testing (Grade 1B), venography (Grade 1B), or whole-leg US (Grade 2B). In patients with moderate pretest probability, we recommend initial testing with a highly sensitive D-dimer, proximal compression US, or whole-leg US rather than no testing (Grade 1B) or venography (Grade 1B). In patients with a high pretest probability, we recommend proximal compression or whole-leg US over no testing (Grade 1B) or venography (Grade 1B).

CONCLUSIONS

Favored strategies for diagnosis of first DVT combine use of pretest probability assessment, D-dimer, and US. There is lower-quality evidence available to guide diagnosis of recurrent DVT, upper extremity DVT, and DVT during pregnancy.

Ultrasound screening for asymptomatic deep vein thrombosis after major orthopaedic surgery: the VENUS study

BACKGROUND

Venography is currently used to assess the incidence of deep vein thrombosis (DVT) in dose-finding and confirmatory trials of new antithrombotic agents. Centrally adjudicated, complete compression ultrasound (CCUS) could be a non-invasive alternative to venography.

OBJECTIVES

A substudy of two, similarly designed, phase IIb trials of a novel, oral anticoagulant for the prevention of venous thromboembolism after elective hip or knee arthroplasty was undertaken to validate CCUS against venography.

PATIENTS/METHODS

Patients received study drugs until mandatory, bilateral venography was performed 7 +/- 2 days after surgery. CCUS was performed within 24 h after venography by sonographers blinded to the venography result. Sonographers were trained and certified for the standardized examination and documentation procedure. Venograms and sonograms were adjudicated centrally at different sites by two independent readers; discrepancies between readers were resolved by consensus.

RESULTS

A total of 1104 matching pairs of evaluable venograms and sonograms were obtained from the participants of the two trials (n = 1435): 19% of venograms and 20% of sonograms were not evaluable. The observed frequency of any DVT was 18.9% with venography and 11.5% with CCUS. Sensitivity of CCUS compared with venography was 31.1% for any DVT (95% confidence interval 23.4, 38.9), 21.0% (2.7, 39.4) for proximal DVT, and 30.8% (23.1, 38.6) for distal DVT. The figures for specificity were 93.0% (91.0, 95.1), 98.7% (98.0, 99.5), and 93.3% (91.5, 95.3), respectively.

CONCLUSIONS

Based on these results, centrally adjudicated CCUS will be unable to replace venography for DVT screening early after major orthopaedic surgery in studies evaluating anticoagulant drugs.

Does anticoagulation do more harm than good?: A comparison of patients treated without prophylaxis and patients treated with low-dose warfarin after total knee arthroplasty

A cohort of 785 patients treated without any form of thromboprophylaxis was compared with an identical group of 957 patients treated with 6 weeks of low-dose warfarin. All complications seen within 90 days of surgery were recorded. The control group had a total complication rate of 2.2%, with a death rate from thromboembolic disease of 0.0% and a total death rate of 0.2%. The warfarin group had a total complication rate of 4.7%, with a death rate from thromboembolic disease of 0.0% and a total death rate of 0.1%. Both deaths in the control group were from cardiac disease, while the death in the warfarin group was due to a massive gastrointestinal bleeding. The warfarin group had twice the infection rate of the control group.

Thrombus precursor protein, endogenous thrombin potential, von-Willebrand factor and activated factor VII in suspected deep vein thrombosis: is there a place for new parameters?

Because of its high negative predictive value, D-Dimer is an important parameter in the exclusion of deep vein thrombosis (DVT) but it produces a high number of false-positive results. We therefore evaluated different blood parameters in 74 consecutive patients with suspected DVT, whose final diagnosis was based on the results of Duplex ultrasound or venography. DVT was diagnosed in 52.7%. While D-Dimer, thrombin-antithrombin complexes, prothrombin fragment 1+2, von-Willebrand factor and thrombus precursor protein were significantly increased in patients with DVT, there was no influence concerning endogenous thrombin potential and activated factor VII. There was no significant correlation between the thrombus extension or the duration of symptoms with any of these parameters. D-Dimer showed the best sensitivity (94.9%) to specificity (45.7%) ratio and neither the sole nor the additional evaluation of any other investigated parameter increased its diagnostic performance. We, therefore, conclude that the determination of D-Dimer remains the 'gold standard' in the laboratory testing of patients with suspected DVT.

C-reactive protein in the diagnosis of deep vein thrombosis

The role of C-reactive protein (CRP) in the diagnosis of suspected deep vein thrombosis (DVT) and a possible advantage of its additional evaluation with D-dimer has not been clearly evaluated. We therefore studied plasma CRP and D-dimer levels in 233 consecutive patients with suspected DVT; the final diagnosis was based on the results of colour duplex ultrasound or venography. DVT was diagnosed in 31.3%. CRP and D-dimer correlated significantly (r = 0.64, P < 0.01); both were increased significantly in patients suffering from DVT (P < 0.001). Multivariate analysis revealed a significant influence of the presence of DVT (P < 0.001), the presence of malignancy (P < 0.001) and the presence of inflammatory diseases (P = 0.009) on plasma CRP, while there was no significant influence of the duration of symptoms (P = 0.30). The sensitivity (75% vs 93%) to specificity (69% vs 55%) relationship showed inferior results for CRP compared with D-dimer; its additional evaluation did not improve the diagnostic value of D-dimer. We conclude that CRP can provide additional information neither for the diagnostic process in patients with suspected DVT nor for the differential diagnosis of DVT and inflammatory diseases.

Ultrasound with Levovist in the diagnosis of suspected calf vein thrombosis

Diagnosing calf vein thrombosis (CVT) by color Doppler ultrasound (US) is often a difficult task because of swelling or obesity. The purpose of this study was to assess if IV infusion of Levovist can improve the accuracy and reduce the rate of indeterminate examinations. A total of 20 patients with suspected CVT underwent color Doppler US without and with Levovist followed by ascending venography as the "gold standard," which detected calf clots in 7 patients (35%). Compared to routine noncontrast sonography, Levovist examination reduced the rate of indeterminate scans from 55% to 20% and improved the specificity for the detection of CVT from 25% to 67% without compromising sensitivity (100% to 86%) notably. Image quality was improved in 13 (65%) of 20 scans. In conclusion, we can say that Levovist improves the quality of duplex examination of the calf veins, especially in cases with difficult conditions due to obesity or swelling.

Pathophysiology and diagnosis of deep venous thrombosis

Lower-limb deep venous thrombosis (DVT) affects between 1% to 2% of hospitalized patients. These thrombi disrupt the vascular integrity of the lower limbs and are the source of emboli that kill approximately 200,000 patients each year in the United States. The causes of thrombosis include vessel wall damage, stasis or low flow, and hypercoagulability. These factors favor clot formation by disrupting the balance of the opposing coagulative and fibrinolytic systems. The symptoms and signs of venous thrombosis are caused by obstruction to venous outflow, vascular inflammation, or pulmonary embolization. About 70% of patients referred for clinically suspected venous thrombosis, however, do not have the diagnosis confirmed by objective testing. Among the 30% who have venous thrombosis, about 85% have proximal vein thrombosis, and the remainder have thrombosis confined to the calf. Physicians cannot rely on signs and symptoms to make the diagnosis of DVT and must depend on imaging studies to guide treatment. Patients with proximal vein thrombosis who are inadequately treated have a 47% frequency of recurrent venous thromboembolism over 3 months. In contrast, clinically detectable recurrence occurs in less than 2% of patients with proximal vein thrombosis if an adequate anticoagulant response is achieved. Of the diagnostic procedures for DVT, venography is the only invasive test of proven value, and ultrasonographic (US) studies are the most commonly used noninvasive modaity. Other procedures are occasionally used to diagnose DVT, including impedance plethysmography, computed tomography, and magnetic resonance imaging. US examinations are noninvasive, they are rapidly obtained, and they can be performed serially. In symptomatic patients, venous US is sensitive and specific for proximal DVT; however, US is insensitive to calf vein thrombosis and to asymptomatic DVT occurring after surgery. Patients with symptoms of recurrent DVT also can present a difficult diagnostic problem. Only about 20% to 30% of these individuals actually have the disease; the rest have symptoms arising from chronic venous insufficiency or from any of the causes of lower extremity pain. After an acute episode, up to 50% of patients have compression ultrasound abnormalities for 6 months that are indistinguishable from the original findings of DVT. Hence, there are a significant number of patients and clinical circumstances in which the diagnosis of DVT is difficult. 99mTc-radiolabeled peptides that target the molecular biology of thrombosis should aid in the management of the disease, particularly in asymptomatic patients at high risk, in patients with recurrent symptoms, in patients with active DVT in the calf and/or pelvis, and in patients with intermediate- or low-probability lung scans.

Oedema in the lower limb of patients with chronic critical limb ischaemia (CLI)

OBJECTIVE

approximately 70% of patients with chronic critical limb ischaemia (CLI) show clinical signs of oedema in the distal leg and foot. The primary aim of the present investigation was to quantify this oedema. In addition we investigated whether oedema formation could be due to deep venous thrombosis (DVT).

METHODS

fifteen patients with unilateral CLI and oedema were studied, four males and 11 females, with a mean age of 77+/-10.3 years. Water displacement volumetry (WDV) was used to measure limb volume. Colour duplex ultrasound (CDU) and venous occlusion plethysmography (VOP) were applied to exclude functionally significant DVT. Blood chemistry was analysed to screen for some causative factors of generalised oedema formation.

RESULTS

the mean volume of the limbs with CLI was 9% greater than the contralateral limbs (1279+/-325 ml vs. 1179+/-298 ml). None of the patients had functionally significant DVT. The mean plasma albumin concentration was reduced at 28.5+/-6.6 g/l.

CONCLUSION

a significantly reduced plasma albumin concentration cannot be regarded as a causative factor, since the oedema is unilateral. The aetiology of oedema formation is probably multifactorial, and further investigations are under progress to elucidate relevant pathogenetic factors.

Early development of deep-vein thrombosis following hip fracture surgery: the role of venous wall thickening detected by B-mode ultrasonography

Deep-vein thrombosis (DVT) remains the most frequent complication following hip surgery. This study was designed in order to evaluate the development of DVT after hip fracture surgery, and to determine if venous wall thickening detected before surgery predisposes patients to postoperative DVT. Systematic ultrasound examinations were performed on 100 consecutive patients undergoing hip fracture surgery on the day preceding the operation, and then postoperatively on days 2, 5 and 10. A total of 12 proximal, 28 distal deep-vein and four saphenous vein thromboses were detected. Of the DVT, 19 (43%) were detected at day 2. Five out of eight patients with venous wall thickening had a previous history of DVT. Venous wall thickening was positively correlated with proximal DVT development (62.5% versus 8% incidence in the group of patients with and without venous wall thickening respectively; p<0.001, relative risk = 7.8). This study highlights the high frequency of early major thromboembolic events following hip fracture surgery. It is considered that patients with a previous history of venous thromboembolic disease should undergo B-mode ultrasonographic examination before hip fracture surgery. Patients in whom venous wall thickening is detected should have repeated postoperative ultrasonographic examinations enabling early detection of DVT.

Utility of leg ultrasonography in suspected symptomatic isolated calf deep venous thrombosis

PURPOSE

To evaluate the utility of duplex ultrasonography in patients with suspected symptomatic, isolated calf deep venous thrombosis.

PATIENTS AND METHODS

Thirty patients with clinically suspected isolated calf deep venous thrombosis were examined with both duplex ultrasonography and contrast venography and the results were compared.

RESULTS

Venography detected 7 cases of isolated calf deep venous thrombosis, all of which were also detected by ultrasonography. Ultrasound identified an additional 3 cases of soleal vein thrombosis, but venography did not visualize these veins. Of the 20 negative ultrasound studies, 11 were technically inadequate; however, no false-negative ultrasound studies were noted.

CONCLUSIONS

Compression ultrasonography may be reliable for the evaluation of patients with suspected symptomatic infrapopliteal deep venous thrombosis. Its apparent superiority to contrast venography in visualizing muscular calf veins warrants further study; however, the high rate of technical inadequacy in ultrasound studies observed here, if confirmed in larger studies, may limit the usefulness of ultrasound in this setting.

Can laboratory testing improve screening strategies for deep vein thrombosis at an emergency unit?

OBJECTIVES

To study various markers of blood coagulation and fibrinolysis in relation to the extension of deep vein thrombosis (DVT), and to compare the diagnostic usefulness of these markers as screening tests for excluding DVT.

DESIGN

A clinical study of patients admitted to an emergency unit.

SETTING

Ostra Hospital, Göteborg, Sweden.

SUBJECTS

One hundred and five patients with a clinical suspicion of DVT.

MAIN OUTCOME MEASURES

Phlebography was used as the reference method for a diagnosis of DVT. Small distal thromboses as well as large proximal thromboses were included. Plasma D-dimer as well as other markers of coagulation and fibrinolysis were analysed.

RESULTS

Twenty-eight proximal and 20 distal DVTs were found. Plasma D-dimers (one ELISA and two latex assays), fibrin monomer, prothrombin fragment 1 + 2 (F1+2), thrombin-antithrombin III complex (TAT) and the t-PA-PAI-1 complex were all significantly correlated to the extension of DVT, whilst fibronectin, tissue-type plasminogen activator (t-PA), single-chain urokinase-type plasminogen activator (scru-PA) and plasminogen activator inhibitor 1 (PAI-1) were not. The sensitivity was 94% for the D-dimer ELISA and one of the latex methods (latex-B), at a specificity of 60% and 68%, respectively. The negative predictive value was 92% for ELISA and 93% for latex-B, and both assays showed a negative predictive value of 100% for proximal DVTs. Fibrin monomer, F1+2, TAT, D-dimer (latex-S) and the t-PA-PAI-1 complex all showed lower negative predictive values (88, 84, 79, 78 and 65% respectively).

CONCLUSIONS

Sensitivity and negative predictive values for a latex assay (D-dimer latex-B) was similar to that of a D-dimer ELISA: With a sensitivity of 94% (100% for proximal DVTs) such a latex assay may be included in a screening strategy for DVT at an emergency unit. However, the safety of such an approach has to be tested in other prospective studies.