Biomedical subjects

A W Lensing

Publications and source records attributed to A W Lensing.

At least 37 records · Page 2Linked to original sources

PubMed1998

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.

Diagnostic Techniques and Procedures↗

PubMed1998

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.

Diagnosis, Differential↗

PubMed1998

Low molecular weight heparin versus unfractionated heparin in the initial treatment of venous thromboembolism.

In this review, we analyze data from randomized trials in which low molecular weight heparin was compared with unfractionated heparin, both to estimate the treatment effect of low molecular weight heparin in the initial treatment of venous thromboembolism and to evaluate the effect of the varied proportion of included cancer patients (6% to 22.7%) on the incidence of outcome events (recurrence of venous thromboembolism, bleeding, and mortality) and on the estimated treatment effect. Low molecular weight heparin has been extensively investigated in patients with deep vein thrombosis, but few trials have included patients with pulmonary embolism. The risk of recurrence of venous thromboembolism (odds ratio, 0.77; 95% CI, 0.56-1.04), major bleeding (odds ratio, 0.60; 95% CI, 0.38-0.95), and mortality (odds ratio, 0.72; 95% CI, 0.55-0.96) was less with low molecular weight heparins compared with unfractionated heparin. The proportion of cancer patients in these studies had a statistically significant effect on the incidence of recurrent venous thromboembolism (P = 0.03) and mortality (P = 0.002), but no influence on the estimated treatment effects of low molecular weight heparins. Low molecular weight heparin is effective and safe in the initial treatment of venous thromboembolism.

Anticoagulants↗

PubMed1998

Surrogate endpoints for the assessment of efficacy in venous thromboembolism treatment trials.

For the assessment of the efficacy of anticoagulant therapy in patients with symptomatic venous thrombosis, the incidence of symptomatic venous thromboembolic complications is the outcome measure of choice. However, the low incidence of such complications necessitates the inclusion of a prohibitively large number of patients in randomized trials evaluating anticoagulant regimens. Therefore, alternative efficacy outcome measures are desirable. This paper discusses the validity of the following alternative tests: venography and compression ultrasound for deep vein thrombosis; and pulmonary angiography and perfusion lung scanning for pulmonary embolism. It is concluded that a combination of one of the deep vein thrombosis tests and perfusion lung scanning is the optimal approach. A thrombotic burden assessment, using repeat venography and perfusion lung scanning, has been performed at the end of treatment (day 10) with low-molecular-weight heparin and unfractionated heparin in 170 patients with symptomatic proximal deep vein thrombosis. An improved thrombotic burden was associated with a low number of subsequent symptomatic venous thromboembolic complications (4%), whereas this figure gradually increased for patients with an unchanged (10%) and deteriorated (29%) outcome (p < 0.005). It is concluded that the thrombotic burden assessment has potential to replace symptomatic outcomes, especially in dose-finding studies.

Anticoagulants↗

PubMed1998

Long-term outcomes after deep venous thrombosis of the lower extremities.

Few natural history studies are available which describe long-term outcomes after venous thromboembolism. However, symptomatic deep-vein thrombosis (DVT) of the lower extremities carries a high risk for recurrent venous thromboembolism that persists for many years. This risk is higher among patients with permanent risk factors including inherited abnormalities of hemostasis than among patients who have suffered trauma or who are postoperative. The development of recurrent ipsilateral DVT carries a high risk for severe post-thrombotic syndrome, an otherwise rare problem in patients with a first episode of DVT adequately treated with anticoagulant drugs and wearing vascular compression stockings. Long-term survival following DVT is generally good in the absence of malignancy. Carefully designed randomized trials are needed to determine whether chronic anticoagulation can reduce further the risks of recurrent DVT and symptoms of post-thrombotic syndrome.

Anticoagulants↗

PubMed1997

A comparison of compression ultrasound with color Doppler ultrasound for the diagnosis of symptomless postoperative deep vein thrombosis.

BACKGROUND: Despite advances in primary prophylaxis, venous thromboembolism still occurs in a considerable number of high-risk surgical patients. Screening with conventional ultrasound imaging to detect asymptomatic deep vein thrombosis (DVT) has been suggested as a strategy to improve management of such patients, but it is insufficiently sensitive. We evaluated the ability of color Doppler ultrasound to improve the sensitivity of compression ultrasound in the detection of asymptomatic DVT in high-risk orthopedic patients. METHODS: We prospectively evaluated bilateral compression and color Doppler ultrasound measurements of the entire leg in 204 consecutive patients who underwent elective hip or knee replacement surgery, using contrast venography as the reference test. The sensitivity, specificity, and positive predictive value of the ultrasonography tests were determined. RESULTS: The sensitivity, specificity, and positive predictive value (with 95% confidence intervals [CIs]) of compression ultrasound for the detection of proximal DVT were 60% (39%-81%), 96% (92%-99%), and 71% (48%-89%) respectively. The sensitivity, specificity, and positive predictive value (with 95% CIs) of compression ultrasound for the detection of calf vein thrombosis were 33% (18%-52%), 91% (83%-96%), and 58% (34%-80%), respectively. Color Doppler ultrasonography did not identify any additional proximal or calf vein thrombi to those detected by compression ultrasound alone. The sensitivity for all thrombi was 47% (95% CI, 34%-61%) with a positive predictive value of 65% (95% CI, 48%-79%). CONCLUSIONS: Color Doppler ultrasonography has a moderate to low accuracy for the detection of DVT in patients who have had hip and knee replacement surgery. Color Doppler ultrasonography does not increase the detection rate for asymptomatic DVT over compression ultrasound and thus cannot be recommended as a screening test in this setting.

Hip Prosthesis↗

PubMed1997

The risk of recurrent venous thromboembolism in patients with an Arg506-->Gln mutation in the gene for factor V (factor V Leiden).

BACKGROUND: A recently discovered mutation in coagulation factor V (Arg506-->Gln, referred to as factor V Leiden), which results in resistance to activated protein C, is found in approximately one fifth of patients with venous thromboembolism. However, the risk of recurrent thromboembolism in heterozygous carriers of this genetic abnormality is unknown. METHODS: We searched for factor V Leiden in 251 unselected patients with a first episode of symptomatic deep-vein thrombosis diagnosed by venography. The patients were followed prospectively for a mean of 3.9 years to determine the frequency of recurrent venous thrombosis and pulmonary embolism. RESULTS: Factor V Leiden was found in 41 of the patients (16.3 percent; 95 percent confidence interval, 11.8 to 20.9 percent). The cumulative incidence of recurrent venous thromboembolism after follow-up of up to eight years was 39.7 percent (95 percent confidence interval, 22.8 to 56.5 percent) among carriers of the mutation, as compared with 18.3 percent (95 percent confidence interval, 12.3 to 24.3 percent) among patients without the mutation (hazard ratio, 2.4; 95 percent confidence interval, 1.3 to 4.5; P<0.01). CONCLUSIONS: The risk of recurrent thromboembolic events is significantly higher in carriers of factor V Leiden than in patients without this abnormality. Large trials assessing the risk-benefit ratio of long-term anticoagulation in carriers of the mutation who have had a first episode of venous thromboembolism are indicated.

Adult↗

PubMed1997

The natural history of deep-vein thrombosis.

Symptomatic deep vein thrombosis (DVT) carries a high risk for recurrent venous thromboembolism that persists for many years. This risk is dependent on readily identifiable risk factors, being low after a trauma or a surgical intervention, and higher in all the other patient categories. Severe post-thrombotic manifestations seem related with ipsilateral recurrence of DVT but are rare in patients with a first episode of venous thrombosis adequately treated with anticoagulant drugs and wearing compression elastic stockings. In the absence of malignancy, the prognosis with regard to survival is good.

Humans↗

PubMed1997

Diagnostic strategies for the management of patients with clinically suspected deep-vein thrombosis.

Given the perceived inaccuracy of clinical diagnosis, patients with suspected deep vein thrombosis should have objective testing. Due to the inherent limitations of the reference method (contrast venography), several diagnostic strategies using noninvasive tests have been developed. These strategies share two components: anticoagulant therapy is initiated only in patients with an abnormal test, and serial testing is performed in patients with an initial normal test result. A thorough search of the literature was done to identify all studies that have evaluated the feasibility, accuracy, and safety of diagnostic strategies in patients with clinically suspected deep vein thrombosis. The safety of the individual diagnostic strategies was expressed as the total rate of venous thromboembolic complications. Feasibility was expressed as the mean number per patient of extra visits to the hospital and additional tests per patient. A total of 12 reports qualified for the analysis. The diagnostic strategies included venography, serial impedance plethysmography with and without 125I-fibrinogen leg scanning, serial ultrasound imaging with and without D-dimer determination, serial ultrasound imaging in combination with a clinical score, and a diagnostic work-up including ultrasound imaging, impedance plethysmography, D-dimer determination, and a clinical score. The observed venous thromboembolic complication rates varied between 0.4% and 2.6%. Feasibility was lowest for the initial serial impedance plethysmography strategy (mean number of extra hospital visits and mean number of additional tests, 4.1 per patient). Strategies that used the D-dimer test complimentary to ultrasound imaging or the combination of impedance plethysmography and a clinical score performed best (mean number of extra hospital visits and mean number of additional tests, approximately 0.3 per patient). All available noninvasive diagnostic strategies are as accurate and safe as contrast venography for the treatment of patients with clinically suspected deep vein thrombosis. The recently introduced simplified diagnostic strategies allow treatment decisions to be made on the day of presentation in most patients.

Anticoagulants↗

PubMed1997

Newly diagnosed malignancy in patients with venous thromboembolism. Search or wait and see?

The incidence of newly diagnosed malignancy is increased in patients with unexplained venous thromboembolism during the first year after a thromboembolic event in comparison to controls (odds ratio, 3.9-36). Extensive screening with computed tomography, endoscopy and tumor markers can identify most of these undetected malignancies. However, approximately half of these can also be identified based on a simple clinical evaluation. Extensive screening has no demonstrated benefit and might actually cause harm. This consideration, combined with the economical and psychological costs of extensive screening leads to the decision not to use such screening procedures, unless indicated by clinical circumstances. Thus, it is appropriate to maintain a low threshold of suspicion for malignancy when treating patients with unexplained venous thromboembolism and to base the decision to perform additional diagnostic tests on the findings of an initial medical history, physical examination, routine laboratory tests and chest x-ray.

Clinical Trials as Topic↗

PubMed1997

Bleeding classification in clinical trials: observer variability and clinical relevance.

To evaluate the bleeding classification in a recent trial on venous thrombosis treatment, a selection of reported bleeding episodes was adjudicated twice by an independent committee and graded by the treating physician and independent clinical experts on the clinical severity and impact on the patient's life. The kappa values for the dichotomy major bleeding versus minor or no bleeding were 0.79 (95% CI, 0.57-1.0) for the agreement between the two members of the adjudication committee and 0.77 (95% CI, 0.52-1.0) for the agreement between both adjudication sessions. The kappa values for the dichotomy major or minor bleeding versus no bleeding were 0.42 and 0.44. The weighted kappa values for the agreement between the treating physician and the independent experts were 0.76 for the clinical severity and 0.79 for the impact on the patient's life (95% CI, 0.63-0.88 and 0.70-0.89). The association between the adjudication result expressed as major bleeding or minor or no bleeding and the clinical grading by the treating physician resulted in an ROC curve with an area under the curve of 0.98 for the clinical severity and 0.99 for the impact on the patient's life. The dichotomy major or minor bleeding versus no bleeding resulted in areas under the curve of 0.70 and 0.66. In conclusion, the applied criteria for major bleeding are reproducible and clinically relevant. The criteria for minor bleeding are not reproducible and are less associated with the observed clinical relevance.

Clinical Trials as Topic↗

PubMed1996

The long-term clinical course of acute deep venous thrombosis.

BACKGROUND: In patients who have symptomatic deep venous thrombosis, the long-term risk for recurrent venous thromboembolism and the incidence and severity of post-thrombotic sequelae have not been well documented. OBJECTIVE: To determine the clinical course of patients during the 8 years after their first episode of symptomatic deep venous thrombosis. DESIGN: Prospective cohort study. SETTING: University outpatient thrombosis clinic. PATIENTS: 355 consecutive patients with a first episode of symptomatic deep venous thrombosis. MEASUREMENTS: Recurrent venous thromboembolism, the post-thrombotic syndrome, and death. Potential risk factors for these outcomes were also evaluated. RESULTS: The cumulative incidence of recurrent venous thromboembolism was 17.5% after 2 years of follow-up (95% CI, 13.6% to 22.2%), 24.6% after 5 years (CI, 19.6% to 29.7%), and 30.3% after 8 years (CI, 23.6% to 37.0%). The presence of cancer and of impaired coagulation inhibition increased the risk for recurrent venous thromboembolism (hazard ratios, 1.72 [CI, 1.31 to 2.25] and 1.44 [CI, 1.02 to 2.01], respectively). In contrast, surgery and recent trauma or fracture were associated with a decreased risk for recurrent venous thromboembolism (hazard ratios, 0.36 [CI, 0.21 to 0.62] and 0.51 [CI, 0.32 to 0.87], respectively). The cumulative incidence of the post-thrombotic syndrome was 22.8% after 2 years (CI, 18.0% to 27.5%), 28.0% after 5 years (CI, 22.7% to 33.3%), and 29.1% after 8 years (CI, 23.4% to 34.7%). The development of ipsilateral recurrent deep venous thrombosis was strongly associated with the risk for the post-thrombotic syndrome (hazard ratio, 6.4; CI, 3.1 to 13.3). Survival after 8 years was 70.2% (CI, 64.7% to 75.6%). The presence of cancer increased the risk for death (hazard ratio, 8.1; CI, 3.6 to 18.1). CONCLUSION: Patients with symptomatic deep venous thrombosis, especially those without transient risk factors for deep venous thrombosis, have a high risk for recurrent venous thromboembolism that persists for many years. The post-thrombotic syndrome occurs in almost one third of these patients and is strongly related to ipsilateral recurrent deep venous thrombosis. These findings challenge the widely adopted use of short-course anticoagulation therapy in patients with symptomatic deep venous thrombosis.

Adult↗

PubMed1995

[Thrombosis of the cerebral veins and sinuses in 62 patients].

OBJECTIVE: Analysis of signs, symptoms, course and treatment of patients with cerebral venous and sinus thrombosis (CVST). DESIGN: Retrospective study. SETTING: Neurological departments of Dutch teaching hospitals. METHOD: Analysis of data of patients admitted to the neurological wards of nine teaching hospitals, diagnosed from 1970 to 1990. All patients with a clinical diagnosis of CVST, confirmed by X-ray angiography, magnetic resonance imaging, surgery or autopsy were included. Patients with cavernous sinus thrombosis were excluded. The clinical condition of patients after 3 months was scored on a 4-point scale. RESULTS: Of 93 patients 62 fulfilled the inclusion criteria. Three months after the diagnosis 41 patients (66%) had recovered, 10 patients (16%) were seriously disabled, 11 patients (18%) had died. Factors associated with a poor outcome were coma (relative risk 3.5) and hemiparesis (relative risk 2.3) at the time of diagnosis. Signs of cerebral haemorrhage or infarction (by computed X-ray tomography) were associated with disability or death. Anticoagulant treatment was not significantly associated with a better or poorer outcome in these patients. CONCLUSION: This study confirms the variations in causes, clinical presentation, natural history, and treatment of CVST. No conclusion could be drawn about the effect of anticoagulant treatment.

Anticoagulants↗

PubMed1995

Accuracy of clinical assessment of deep-vein thrombosis.

The clinical diagnosis of deep-vein thrombosis is generally thought to be unreliable. From experience, we hypothesised that this widely held view might be incorrect. We developed a clinical model and prospectively tested its ability in three tertiary care centres to stratify symptomatic outpatients with suspected deep-vein thrombosis into groups with high, moderate, or low probability groups of deep-vein thrombosis. We evaluated our clinical model in combination with venous ultrasonography to determine the potential for an improved and simplified diagnostic approach in patients with suspected deep-vein thrombosis. All patients were clinically assessed to determine the probability for deep-vein thrombosis before they had ultrasonography and venography. All tests were performed and interpreted by independent observers. In 529 patients, the clinical model predicted prevalence of deep-vein thrombosis in the three categories: 85% in the high pretest probability category, 33% in the moderate, and 5% in the low category. There was no statistical difference in the performance of the model in the three centres. The model demonstrated excellent interobserver reliability (Kappa = 0.85). There were important differences with ultrasonography between the high and low pretest probability groups for both positive predictive values (100% (95% CI, 94-100%) vs (63% [35-85%], respectively). Thus, use of the clinical model combined with ultrasonography would decrease the number of false positive and negative diagnosis if venography were done when the ultrasound result and pretest probability were discordant. The diagnostic process could be simplified by excluding those patients with low pretest probability and normal ultrasound results from serial testing.

Decision Trees↗

PubMed1995

Treatment of deep venous thrombosis with low-molecular-weight heparins. A meta-analysis.

BACKGROUND: An intravenous course of unfractionated heparin adjusted on the basis of the activated partial thromboplastin time is the initial treatment of choice for most patients with venous thromboembolism. Recently introduced low-molecular-weight heparin preparations can be administered subcutaneously, once or twice daily, without laboratory monitoring. We quantitatively assessed the relative efficacy and safety of low-molecular-weight heparin vs standard heparin for the initial treatment of deep venous thrombosis. METHODS: English-language reports of randomized trials were identified through a MEDLINE search (1984 through 1994) and a complementary extensive manual search. Reasons for exclusion from the analysis were no heparin dosage adjustments, the lack of use of objective tests for deep venous thrombosis, duplicate reports, preliminary reports of data later presented in full, dose-ranging studies that used higher doses of low-molecular-weight heparin than are currently in use, and the failure to provide blind end-point assessment. We assessed the incidence of symptomatic recurrent venous thromboembolic disease, the incidence of clinically important bleeding, and mortality. RESULTS: Ten of the 19 identified trials satisfied the predetermined criteria. The relative risk reductions for symptomatic thromboembolic complications (53% [95% confidence interval, 18% to 73%]), clinically important bleeding (68% [95% confidence interval, 31% to 85%]), and mortality (47% [95% confidence interval, 10% to 69%]) were all statistically significantly in favor of low-molecular-weight heparin. CONCLUSIONS: Low-molecular-weight heparins administered subcutaneously in fixed doses adjusted for body weight and without laboratory monitoring are more effective and safer than adjusted-dose standard heparin. Since low-molecular-weight heparins may not be interchangeable and the conclusions of our meta-analysis are based mainly on the findings of three trials that used two different low-molecular-weight heparins, definitive randomized controlled trials for the other low-molecular-weight heparins are required.

Hemorrhage↗

PubMed1995

Accuracy of ultrasound for the diagnosis of deep venous thrombosis in asymptomatic patients after orthopedic surgery. A meta-analysis.

OBJECTIVE: To evaluate, by meta-analysis, the accuracy of ultrasound screening for deep venous thrombosis in patients after orthopedic surgery. DATA SOURCES: The MEDLINE database from January 1982 to October 1993. Bibliographies of retrieved articles and recent journal publications were searched independently and using Current Contents. STUDY SELECTION: All articles evaluating the use of venous ultrasound imaging (B-mode, duplex, and color Doppler) compared with standard contrast venography for detecting deep venous thrombosis. We excluded abstracts, early reports of studies later reported in full, and studies in which venography was not done in all patients. Seventeen of 30 identified studies were eligible. DATA EXTRACTION: Eligible articles were reviewed for the presence of three key criteria necessary for evaluating the accuracy of the diagnostic tests: 1) previously established objective criteria for venography and ultrasound, 2) independent blinded comparisons of venography and ultrasound, and 3) prospective evaluations of consecutive patients. Studies including all three key criteria were defined as level 1 (minimized bias) studies; otherwise, they were defined as level 2 studies. DATA SYNTHESIS: In level 1 studies, ultrasonography had a sensitivity of 62% (95 of 153; 95% CI, 54% to 70%), a specificity of 97% (CI, 96% to 98%), and a positive predictive value of 66% (95 of 144; CI, 58% to 74%) for detecting proximal thrombi. For level 2 studies, the sensitivity was 95% (CI, 87% to 99%), the specificity was 100% (CI, 99% to 100%), and the positive predictive value was 100% (CI, 94% to 100%). Differences between level 1 and level 2 studies appeared to be related to bias in study design. CONCLUSIONS: Venous ultrasound imaging has only moderate sensitivity and a moderate positive predictive value when used to screen for deep venous thrombosis in patients after orthopedic surgery; thus, ultrasound imaging may have limitations as a screening test.

Aged↗

PubMed1995

Comparison of the accuracy of impedance plethysmography and compression ultrasonography in outpatients with clinically suspected deep vein thrombosis. A two centre paired-design prospective trial.

Impedance plethysmography (IPG) and compression ultrasonography (CUS) have been reported to be highly accurate for the diagnosis of deep vein thrombosis (DVT) in symptomatic patients. In many centres CUS has become the method of choice. However, direct comparisons of the accuracy of IPG to CUS have not been performed. To determine the test of choice we performed a two centre prospective comparison of IPG and CUS, with venography, and determined how the size and distribution of thrombi influenced the accuracy of each test. 495 symptomatic outpatients with suspected DVT had evaluable venograms. The prevalence of DVT was 27% (130/495), 84% (109) of which were proximal. The sensitivity of IPG and CUS for proximal vein thrombosis was 77% and 90% respectively (p = .002). The specificity of IPG was 93% whereas the specificity of CUS was 98% (p = 0.04). There were significant differences in accuracy between the two centres as a consequence of differences in the size and location of thrombi The majority of proximal thrombi not detected by IPG and CUS involved less than 5 cm of the distal half of the popliteal vein and most of these thrombi occurred in one centre. Exclusion of these thrombi from the analysis increases the sensitivity of CUS to 99% (86/87) and IPG to 91% (72/79), for proximal thrombi (P = .019). The positive predictive value of CUS was strongly influenced by the number of abnormal venous segments (three sites were examined); 100% (80/80) if two or three sites were abnormal, but only 68% if a single site was involved. We conclude that: 1) CUS is more accurate than the IPG for the diagnosis of DVT in symptomatic outpatients, and this relationship holds true regardless of the size or location of the DVT, 2) the sensitivities of IPG and CUS are much lower for small proximal DVT, and 3) confirmatory venography is warranted if the abnormality with CUS is limited to one venous segment.

Ambulatory Care↗

PubMed1995

Subcutaneous low-molecular weight heparin or oral anticoagulants for the prevention of deep-vein thrombosis in elective hip and knee replacement? Fraxiparine Oral Anticoagulant Study Group.

OBJECTIVE: To compare efficacy, safety, and feasibility of adjusted-dose oral anticoagulants (OAC) versus fixed-dose subcutaneous low molecular weight heparin (LMWH) for the prevention of deep venous thrombosis (DVT) in patients who have undergone elective hip or knee replacement. DESIGN: Multicentre, single blind randomised trial. OAC (acenocoumarol, target International Normalised Ratio, 2.0-3.0) and LMWH (nadroparine, 60 aXa IU/kg once daily) were started preoperatively and continued for 10 days. All outcome measures were adjudicated by an independent committee unaware of treatment allocation. SUBJECTS: 672 consecutive patients scheduled for elective hip or knee replacement surgery. All patients wore bilateral graduated compression stockings. MAIN OUTCOME MEASURES: The endpoint for the assessment of efficacy was venography confirmed DVT or confirmed symptomatic pulmonary embolism. The endpoint for the assessment of safety was clinically important bleeding during study treatment or within 48 h of the end of treatment. RESULTS: Among the 517 patients with interpretable venograms, 391 had a hip replacement and 126 had a knee implant. DVT was demonstrated in 50 (20%) of 257 patients allocated to OAC and 43 (17%) of 260 patients allocated to nadroparine (p = 0.45), for an absolute difference in DVT incidence of 2.9% in favour of nadroparine (95% CI, -3.7-9.5). Clinically important bleeding occurred in eight (2.3%) of the 342 oral anticoagulant treated patients and in five (1.5%) of the 330 nadroparine treated patients (p = 0.62), for an absolute difference in favour of nadroparine of 0.8% (95% Cl, -1.3-2.9). CONCLUSION: Patients who undergo major orthopaedic operations have a high risk of venous thromboembolism. Once daily fixed-dose subcutaneous nadroparine is at least as efficacious and safe as daily adjusted OAC for prophylaxis against DVT after hip or knee implantation but is more simple to administer.

Administration, Oral↗